On June 21, 1970, in the searing heat of Mexico City, Brazil and Italy faced off in the World Cup final. Each was going for its third crown. Watching on a small black-and-white TV at his home in São Paulo, 9-year-old Miguel Nicolelis sat in awe. His father had purchased the TV just for the Cup. Minutes before the final whistle was blown, eight of the men in yellow-and-green jerseys worked together to create one of the greatest goals in the history of the tournament. Pele had the assist; Carlos Alberto unleashed a phenomenal shot across the box to seal Brazil’s 4-1 win.

The city of São Paulo erupted. Fireworks shook the house; fans flooded the streets. Amid the chaos, Miguel stayed glued to the TV screen, replaying the final goal in his mind. The way those eight players had fallen into sync with scarcely a word or look exchanged — it seemed as though they were an extension of a single being. Like every kid in Brazil, Miguel promised himself he’d someday make it to the World Cup.

Today, he is on the verge of achieving that dream. But Nicolelis, now 53, won’t be playing; he’ll be representing Brazil as a neuroscientist, and he’s hoping to pull off a demonstration straight out of a science fiction movie. On June 12, during the opening ceremony of the 2014 FIFA World Cup, eight paralyzed individuals will come onto the pitch. Seven will be seated in their wheelchairs. One of them, however, will be standing. He’ll walk a few steps toward a soccer ball. When he reaches it, he’ll hitch back his leg and then strike the ball. It may roll only a few feet, but that will be enough to officially kick off the Cup. To accomplish this astonishing feat, all he’ll have to do is think about walking. A bionic exoskeleton controlled by his mind will do the rest.

Nicolelis, who developed the exoskeleton and the technology it uses to communicate with a patient’s brain, says it works based on the same concept that drove the 1970 championship team: The mind treats the exoskeleton as an extension of the physical body. For the paralyzed man walking, his brain will essentially think of the exoskeleton as a set of legs; for Pele, his brain thought of the ball as an extension of his feet. This is more than some Zen theory — it’s science based on Nicolelis’s years of research on neuroplasticity, the principle that the brain can rewire itself to adapt to new circumstances and incorporate elements of the world around us.

Long before humans could try out the exoskeleton, it was pioneered by a group of monkeys in Nicolelis’s Duke University lab. He plans his experiments from a two-room office with floor-to-ceiling windows whose white vinyl blinds he never opens. His desk is a jumble of Christmas cards, sketches of the exoskeleton, a DARPA award for excellence, and, of course, a pair of soccer balls. Behind Nicolelis is a photo of a man holding a monkey in his arms like a father might cradle his 5-year-old child. “This is one of the greatest American scientists of the last 50 years,” he tells me. “Jon Kaas.”

In the 1980s, Kaas’s research on neuroplasticity laid the groundwork for Nicolelis’s achievements today. For centuries, medical students learned that once the brain becomes fully developed, it stops changing (until it begins to deteriorate with age). They also learned that different parts of the brain were responsible for different functions (the motor cortex controls movement, the hippocampus handles memory, and so on). It was believed that individual neurons within those regions were responsible for specific tasks. If the neurons associated with a specific task were damaged, the thinking went, the ability to perform that task was lost. Likewise, if the pathways that transport sensory signals to the brain were damaged, that part of the brain’s power was presumed to be lost forever; the associated neurons couldn’t take on a new role.

It turns out that the brain deserves a little more credit. Through their work with primates, Kaas and fellow researchers proved that the brain is adaptable: If a neuron dies, other neurons can take over its functions. If a pathway is blocked, as happens with spinal cord injuries, new pathways can be formed. The brain won’t function exactly as it did before, but it will function. It might even function more efficiently. This is neuroplasticity.

“[Plasticity] is the basis of everything we do,” Nicolelis said. “[Kaas] is like my godfather, he’s like my hero.”

While Kaas was conducting his early neuroplasticity studies, Nicolelis was working toward his medical degree at the University of São Paulo. Since middle school, he’d planned to become a neurosurgeon. As he neared that goal, however, he was becoming more interested in research. He wondered if it was possible to create a 3-D map of the brain, and he asked his mentor at the time, César Timo-Iaria, where he could pursue this kind of work. Go to the airport, Timo-Iaria told him, then get on a flight to the United States and convince a crazy American to pay for it.

And so Nicolelis left Brazil for a postdoctoral fellowship at Hahnemann University in Philadelphia. He had two suitcases and about $1,200 in cash with him when he landed in New York on February 21, 1989, and he spent $300 on a cab ride to Philadelphia (he was scammed by the driver, who claimed to be part of the Italian mafia and threatened to kill Nicolelis if he didn’t pay the exorbitant price).

Nicolelis’s adviser at Hahnemann was John Chapin, whose research focused on developing sensors that could read the signals from clusters of several of the brain’s cortical neurons at the same time. Previously, neuroscientists used sensors that could only read the signals of individual neurons. This was fine when scientists believed that individual neurons controlled individual tasks. But as plasticity proved that groups of neurons work together, Chapin and Nicolelis wanted to read the signals transmitted by these clusters. Over the next five years, they constructed hair-thin sensors that, when implanted in the brain, could simultaneously read signals generated by dozens of neurons. (Nowadays, there are sensors that read 1,800 at a time.)

At about the same time, two studies showed that research subjects who imagined they were practicing an activity showed performance gains similar to the results of actual, physical practice. Mapping the subjects’ brains determined that this mental practice had strengthened existing synapses and created new ones, meaning the subjects had rewired their brains through thought alone. These findings supported a theory proposed in the 1890s by Spanish Nobel laureate and neuroscience pioneer Santiago Ramón y Cajal, who said, “Any man could, if he were so inclined, be the sculptor of his own brain.” The key to the sculpting, he believed, was mental practice. Cajal was never able to prove it, but a century later, neuroplasticity research backed up his ideas. The same principles became the bedrock of Nicolelis’s studies and helped lead to the development of a mind-controlled exoskeleton.

In 1994, Nicolelis became an assistant professor at Duke University. Over the next few years, he embarked on a series of animal studies that in 1999 produced the first brain-machine interface — a device that lets a person’s brain control the movements of a machine. The BMI reads signals from groups of neurons and translates them into instructions for a machine, similar to the way in which an able-bodied person’s brain sends signals to the spinal cord, then on to the muscles.

BMIs work because our brains generate distinct electrical patterns when we think about doing something. In 90 percent of people, Nicolelis explains, the same neurons fire to create an electrical pattern that tells the body to walk. The brain and spinal cord decode the signal and turn it into a command. In the first successful demonstration of a BMI, Nicolelis and Chapin built sensors that read the brain activity of a rat as it attempted to push a lever that would allow it to get water. Once the BMI recognized the thought pattern for pushing the lever, the BMI processed it, turned it into a command, and sent the command to the lever. The rat was able to visualize the act of pushing the lever and then let the BMI do the rest.

In 2000, Nicolelis and his team embarked on a series of studies demonstrating that an owl monkey could use a BMI to simultaneously control two robotic arms, one at Duke and another 600 miles away in Massachusetts; an adult rhesus monkey could use a BMI to control a video-game joystick; and another monkey could move a computer cursor by imagining that it was moving. In 2004, BMIs were tested in humans for the first time. The study involved 11 patients with Parkinson’s disease who were already scheduled for surgery to receive deep-brain stimulation. Nicolelis’s team gained permission to implant sensors during the procedure. During surgery, Nicolelis had the patients play a video game, and then, with a BMI attached, they learned to control the game with their minds.

In 2008, a few months after Brazil won its bid to host the World Cup, Nicolelis’s group pulled off one of its most famous experiments. They took an adult female rhesus monkey and implanted electrodes in her brain that could read the signals from 250 to 300 neurons at once. While the monkey, named Idoya, walked on a treadmill in Nicolelis’s Duke lab, a 200-pound, 5-foot-tall humanoid robot in Japan was set up to receive the electrical signals from Idoya’s brain. Soon, the robot started moving. The only thing powering its movements were Idoya’s thoughts. Idoya could watch the robot on a TV screen mounted on her treadmill. Stunningly, the robot was receiving the commands from Idoya’s brain faster than Idoya’s own legs. Later, when the monkey stopped moving her legs but kept thinking about walking, the robot kept walking.

These were vital steps on the way to developing an exoskeleton that would allow paralyzed individuals to walk, but one element was still missing: Nicolelis had to figure out how to re-create the sense of touch. When able-bodied people walk, feelings of pressure and movement travel from their feet to the spinal cord and brain. In survivors of partial or full spinal-cord injury, that throughway is damaged beyond repair. Nicolelis found the solution in 2011, when he demonstrated that the brain could interpret signals from mechanical sensors just as readily as it does from the body’s natural sense receptors. The signals can be sent directly to the brain, or they can be routed through other nerves and sense receptors, such as those on the arms. “It’s almost like creating a sixth sense,” he explained in a podcast. “If the pattern is delivered under certain conditions, the brain can really readily learn, in just a few sessions, how to handle this new artificial message — that we call an ‘artificial touch.’” Nicolelis envisioned that this “sixth sense” would enable patients with spinal cord injuries to experience the sensation of their feet touching the ground — sensations that their injuries prevented.

By then, Nicolelis was already dreaming about the possibilities of a mind-controlled exoskeleton. In June 2011, during the Brazilian leg of the tour for his book Beyond Boundaries, Nicolelis decided to make a special announcement during an event at the São Paulo Orchestra Theater. About 10 minutes before walking onstage, he added one more slide to his presentation — a sketch of the exoskeleton. When he showed it, telling the crowd he wanted a paralyzed person to “walk again” at the World Cup, the audience went nuts. He says he hadn’t seen Brazilians that excited since they’d won the 2002 World Cup. It was all the inspiration he needed to form the Walk Again Consortium, a team of 156 scientists and engineers from 25 nations.

The project started gaining attention, but there was still a technological hurdle to clear: For the BMI to work, its sensors had to be surgically implanted in the brain. While this procedure had been proven safe in countless animal subjects and during the 2004 tests with human patients, conducting brain surgery for a World Cup exhibition raised ethical questions. Instead, Nicolelis developed a workaround. In 2012, his Duke lab proved that an electroencephalogram (EEG) sensor cap worn on subjects’ heads could read and transmit brain activity well enough to control the exoskeleton. The EEG cap looks like a swim cap with a pattern of dime-sized holes and black stitching. The sensors are small rings located in the fabric around the holes. Scientists squirt blue gel into the holes to strengthen the connection between the sensors and the neurons. The cap eliminated the need for surgery and carried Nicolelis’s dream one step closer to reality.

Finally, on January 24, 2013, the Brazilian government agreed to fund the project. The Walk Again Consortium had 15 months to make it happen.

In a white-walled, windowless rehabilitation facility a few blocks from Nicolelis’s childhood home in São Paulo, eight participants started training with the BMI in January 2013. Between the ages of 20 and 35 years old, these six men and two women have all been paralyzed below the waist for at least a year. Most were injured in car accidents or falls and all were once able to walk. One was playing soccer with friends when the ball landed on the roof of a nearby building. He climbed up to get it, the roof collapsed, and he hasn’t walked since. When they signed up for what they thought was a rehabilitation study, the patients had no idea it was connected to the World Cup.

The patients’ spinal cords are injured but their brains are healthy. They’re still able to imagine themselves walking, and with the aid of a BMI, lots of concentration, and extensive training, their minds can still generate the right message to propel the body — or an exoskeleton — to walk.

After meeting Nicolelis at Duke in February, I asked to visit the São Paulo lab. He agreed, on the conditions that I could not speak to the participants or include personal information about them. There are strict laws to protect patients’ rights in Brazil, and they include restrictions on media access to patients during clinical trials. With the Brazilian government funding this project, it qualifies as a trial. The participants’ personal stories will be released in 2015, as part of a government-commissioned documentary that has followed the entire process.

At the lab, the patients work with a team of engineers, neuroscientists, and physicians. The staff works 16 to 18 hours per day, seven days a week. Despite the demanding schedule, Nicolelis says, no one complains. They play music to keep their energy and spirits high. “Help!” by the Beatles and the theme song to Mission: Impossible are in heavy rotation. Around 2 a.m., they usually order late-night grub from Chicohamburger, a spot Nicolelis has loved since childhood.

The physicians, most of whom hail from São Paulo, spend the most time with the patients, guiding them through stretching and strengthening exercises. The first step in the training was working with a zero-gravity system, which would hold the patients suspended in the air as a machine moved their legs to get their bodies used to being upright again. One of the patients couldn’t hold back tears as, looking in a mirror, she saw herself standing for the first time in years.

They also used a virtual reality system to teach their brains to interact with the exoskeleton. The training involves wearing a large set of black goggles and the EEG cap to read their brain activity. A small screen inside the goggles shows the patient an animated video of the lower half of a body, so when he tilts his head down, it appears as if he’s looking at his own legs. The aim of the exercise is to make the legs walk. “My goal is that they don’t think about moving the legs of the avatar,” explains Solaiman Shokur, one of the lab’s lead engineers. “That in their brain they are thinking of moving their own legs.” This goes back to neuroplasticity: The patient’s brain has to start treating the avatar as an extension of his physical body. The first time the patients used it, Shokur controlled the legs with a computer program so the patients could get used to the visual. It wasn’t long before the patients adjusted to the equipment and started moving the avatar legs just by thinking about walking. Even Nicolelis was impressed by how fast they mastered it.

One reason for the participants’ success with the virtual reality training was that their brains were receiving sensory feedback from their feet. “The brain is being fooled that the legs are touching the ground, so that they have legs again,” Nicolelis explains. This was made possible thanks to a customized T-shirt designed by Swiss roboticist Simon Gallo. The shirt features three sensors on each arm and a control board on the chest. It interfaces with sensors attached to the patient’s feet that measure data about temperature, pressure, and acceleration. When the left or right foot touches the ground, the sensors on the left or right sleeve vibrate in quick succession. Because the pathways between the nerves in the patients’ arms and their spinal cords have not been damaged, this sensory feedback, which mimics the act of walking, can reach the brain through their arms. “The idea is to feel on your forearm the same movement as heel to toe on the floor,” Shokur says. “It gives the impression of touch and movement.”

As the patients continued to master the virtual reality program, they still didn’t know that they were part of the World Cup exoskeleton project. It’s likely that some were able to guess, since the trials were all over the news, but they weren’t officially informed. They definitely hadn’t seen the exoskeleton, which was still under construction in Paris. In mid-February, Nicolelis made it official. He told his subjects that the exoskeleton was not just for the people in the lab; it was for the entire world.

Even though only one of the participants will get to walk at the opening ceremony, Nicolelis insists that the eight participants see the training as a team effort and not a competition. Lab assistant Nicole Peretti, a biomedical engineering graduate student from California, says there haven’t been any rivalries between patients: “Each gives us feedback and input, and they know that we can’t [help] one without all of them. There’s a sense of community … They know that this research is for all people who are and will be paralyzed. The research is a lot more than June 12.”

The final decision will come down to which patient has been most successful with the technology, Nicolelis says, adding that there have been a few obvious front-runners right from the start. He will keep the participants fully informed throughout the selection process, because, he reiterates, this is not a competition. He has also requested that FIFA allow each patient to demonstrate the exoskeleton at a different game during the Cup, but FIFA has not yet agreed.

After Nicolelis revealed the World Cup plans, the scientists added a new avatar to the virtual reality program. Now, the animated legs look like they belong to a soccer player, with cleats, shin guards, and all. They also added crowd noise to the virtual environment.

In early March, two models of the exoskeleton were shipped from Paris to São Paulo. A couple weeks later, the researchers tested the EEG cap during a match at the Arena de São Paulo, where the opening match will be played. Nicolelis posted the results to Facebook: “Records of brain electrical activity were obtained before, during and after the game … demonstrating that the technology used to obtain brain signals to control the exoskeleton is robust and can work outdoors, in the middle of a stadium, during a football game broadcast.”

I boarded a flight from New York to São Paulo on April 29. As I settled into my seat, the teenager next to me asked why I was traveling to Brazil. “I’m working on a World Cup story,” I said. He cringed. Before I could say more, he began explaining why the government should be spending money on education, not stadiums. An 18-year-old in his final year of high school, he said he should have graduated six months earlier but teacher strikes over the past two years delayed his progress. At that moment, he added, the teachers were striking to protest the Cup. I decided to steer the conversation in another direction: “I’ll actually be interviewing a scientist.”

“Oh, Nicolelis?” he cut in. “I’ve read about his work.”

As a young researcher, Nicolelis left Brazil in search of better opportunities in the United States. He has since made it his mission to inspire Brazilian students to think about careers in science, and to create opportunities for them at home. In the mid-2000s, he convinced the government to build a state-of-the-art neuroscience research facility, a women’s health clinic, and two science-focused elementary schools in one of Brazil’s poorest cities.

“We want kids to think that they can think about science,” Nicolelis explains. “They don’t need to just play soccer.”

Nicolelis had already managed to inspire my seatmate. “I want to do work like his,” the young man told me. Then, as we took off, he added: “[Brazil] doesn’t have a Nobel laureate. He should be the first.”

When I arrived in São Paulo and made my way to Nicolelis’s lab, I was greeted by a security guard who sat in front of the building’s tinted glass doors. A few minutes later, Nicolelis emerged from one of the therapy rooms. He was wearing striped Adidas sandals, white socks, faded jeans, a Palmeiras practice jersey, and a green baseball cap. He looked exhausted.

He shuffled me into his office, explaining that the ministry of health had decided that absolutely no journalists could speak to the patients. “We’re under a, what do you call it? A gag order,” he said. Things were not going perfectly. FIFA had recently narrowed the amount of time allotted for the demonstration. Originally, it was planned for the final minutes between singing the anthems of Brazil and Croatia and starting the game. They’ve since decided to shift Nicolelis’s exhibition to the opening ceremony, which will be held three hours before kickoff. Nicolelis also says that his staff and patients will not have a room inside the stadium to prep.

The uncertainty about the final structure and format of the demonstration has left Nicolelis’s team scrambling to finalize the details. Hanging across from Nicolelis’s desk in São Paulo, there’s a diagram etched on a large whiteboard. In blue marker, it shows the preliminary plans: The selected patient will have one minute and 30 seconds to walk four to eight steps and kick the ball. Many other particulars remain unresolved. Will the patient walk on a raised platform? Will they invite children to stand on the field and represent the next generation of scientists?

As we talked, Nicolelis pulled up photos of some of the famous Brazilians who have visited the lab. Ronaldo, the highest scorer in World Cup history and leader of Brazil’s 2002 championship team, had tried out the virtual reality headset. Former president Luiz Inácio Lula da Silva came for a tour a few weeks earlier. But the visitor Nicolelis was most excited to tell me about was Roberto Rivelino, a star of the 1970 championship team. Nicolelis sounded almost giddy as he relayed Rivelino’s stories of that Cup and playing with Pele.

The next afternoon, I arrived at the same time as one of the patients. As we entered, a physician greeted him with a kiss on the cheek and they disappeared into the therapy room. A second patient was waiting down the hall. When Nicolelis spotted me, he said: “A patient is using the simulator. You want to come?”

The simulator is the step between the virtual reality headset and the exoskeleton. It features motorized legs and arm supports suspended above a treadmill. It holds the patient upright in the same fashion as the exoskeleton, but with more support and a firm back brace rooting it to the ground. The simulator legs move in place, rather than moving forward. The patients first used the simulator to “walk on air,” but now when they use it their feet actually touch the treadmill.

When we entered the room, the patient was already standing inside the contraption, with thick Velcro straps holding his legs into the braces. A physician sat on a nearby stool, holding a remote control that would allow her to stop the machine in case of emergency. An engineer sat at a computer station. “Ready?” he asked in Portuguese. The patient nodded, and the room filled with the sounds of a stadium. The patient concentrated intensely, a look of determination etched across his face. A few seconds passed. A row of small blue LED lights lit up along the rim of a helmet worn on top of the EEG cap, indicating that he was generating the correct thought pattern. Then, his legs started to move. It was working. He was walking — just by thinking about it. A voice, as though coming from a stadium sound system, instructed him in Portuguese, “You have 15 seconds to walk.” And again, he successfully made the exoskeleton walk. He did it four more times.

There was a white sensor attached to the back of his right biceps. This was an electromyography (EMG) sensor reading muscle activity, Nicolelis explained, pointing to a monitor where small lines danced in pyramids as the signals came through. There were also several boxes on the screen that showed his brain activity.

When the patient finished, he flashed a thumbs-up and an exhausted smile. Nicolelis talked to him for a minute before we left the room. As we walked out, I noticed his wheelchair. It was simple, with large wheels and a low back, the kind used in wheelchair sports. Sitting next to this groundbreaking simulator, the chair looked like a relic. It seemed inconceivable that the man I had just seen walking is the same man who uses it every day.

The final step of the process is using the exoskeleton. Eventually, Nicolelis let me see it. Hanging from the ceiling of one of the lab rooms, it was easily double the size of anyone who might use it. The device’s metal braces resemble the outline of a human body, with a thick tangle of exposed hydraulic tubes connecting the back and the legs. The joints are made of metal blocks and clips that look as if they’ve come from a common toolbox. When I got up close, I noticed small square beads with block letters on the ends of the tubes. They looked like the blocks children use to make name bracelets. Nicolelis explained that each set of letters was a code for the engineers, a way to identify different circuits. “You wouldn’t want the message for the hip going to the knee,” he said. Inside the leg braces are black Velcro and plastic harnesses to hold the patients’ legs in place. The battery pack, positioned where the tailbone would be, can last up to two hours. It fuels the 17 generators located directly above the battery, which create force for the legs. The hips are covered in thick, beige plastic.

The engineers sat at computer stations around the room, one working with the algorithm that interprets the participants’ thoughts and another controlling the actual mechanisms of the exoskeleton. When the engineer sitting closest to the exoskeleton pressed a button, the legs started to move, slowly bending and stepping through the air. Inside the exoskeleton, users are able to move about one step per second.

“It takes all of this crazy engineering to replace a tiny segment of the spinal cord,” Nicolelis said with a tinge of amazement. “Imagine how hopeless it would be to create the entire brain.”

On my third day in São Paulo, I arrived at the lab around 6:30 p.m. The quiet inside felt eerie, and all the doors were closed. A few minutes later, I heard a loud round of applause. A patient had successfully controlled the exoskeleton with his mind. He had been the third to complete the task that day. Each patient had walked three sets of six steps. They walked with the support of two engineers to feel more secure. When the third patient finished, according to Nicolelis, “he said it was back like walking the street. He was free again.”

As the scientists recorded data from the tests, the patient wheeled himself into the hallway. Looking worn-out but triumphant, he nodded hello to me, and I smiled in return. That night, Nicolelis treated the team to an upscale Italian dinner at a restaurant called Lellis Trattoria Campinas. Over shared plates of cheesy cannelloni and slices of the dessert quindim, Nicolelis unspooled tales from the conferences he’s attended around the world. On the flight home from one such event, he recalled, one of his sons suggested he watch Elysium. It’s a movie about your exoskeletons, his son said. In the film, Matt Damon’s character goes through a hasty surgery to have an exoskeleton attached to his body and a mind-reading device implanted in his brain.

“It was horrendous!” Nicolelis roared, laughing until his cheeks burned a deep red. Thirty years I’m working on this, he added, and they turn it into this butcher crap! Someone at the table mentioned a few more films, and Nicolelis gave his reviews.

Pacific Rim: “Bad!” Avatar: “Terrible!” James Cameron says he just “dreamed” up that script, Nicolelis added. “Really? Those are soooome dreams.” Surrogates: “The producers called to ask if they could use images of our monkeys. I said no! I don’t want my research associated with that stuff.”

Between fits of laughter, he announced his post–World Cup plans: “I’m telling you, we need a movie — a real movie — about exoskeletons. I’m going to write it.”

Regardless of how they’re depicted in Hollywood, the brain-machine interfaces — and now the exoskeleton — that Nicolelis pioneered are more than science fiction. They hold the potential to help millions of people who’ve suffered life-changing spinal cord injuries. Though clearly not a cure for paralysis, they are certainly a step toward improving quality of life. Shokur told me that at first, he worried that training with the exoskeleton and experiencing what it was like to walk again might give the patients false hope that by the end of the trial period, they could just walk out of the lab. After seeing how the patients responded to the training, however, he realized that wouldn’t be the case. Already, the technology has changed the lives of the eight patients training in São Paulo. The man who became paralyzed during a soccer match can kick a ball again. The woman who hadn’t stood in years now spends time walking in the simulator every week.

The potential medical applications of Nicolelis’s research are vast. In the United States, health care experts have highlighted the therapeutic benefits of using exoskeletons to help paralyzed patients spend more time upright. At the University of Houston, Dr. Jose L. Contreras-Vidal is running a clinical trial with exoskeletons to see how the brain adapts to a BMI. The subjects in his study are stroke survivors and healthy adults. Other exoskeletons are already in use at some U.S. rehab facilities, although these are robotic, not mind-controlled. After the World Cup demonstration, the Brazilian government plans to make Nicolelis’s exoskeletons available at other therapy centers through Brazil’s universal health care system. “We are of course focusing for June on a specific task, but our goal is to have this thing do all sorts of movements,” he explains. “These are just a prototype for what can be developed.”

Contreras-Vidal, the Houston researcher, says he sees the importance of helping patients walk again, but he also voices a concern shared by several scientists: Is the World Cup demonstration too much of a stunt? The focus on kicking a ball, even just on walking, “has the risk of overshadowing all these other things that are even more important,” he says. The attention paid to Nicolelis’s soccer exhibition could come at the expense of understanding the potential for neuroscience and exoskeleton studies to improve more vital functions in paralyzed individuals, like cardiovascular health, skin conditions, bladder function, and more. “This is much bigger than just walking,” Contreras-Vidal says.

Nicolelis has faced criticism before. A researcher at Northwestern University compared one of his studies to a “poor Hollywood science-fiction script.” But for every critic, there are many others who praise Nicolelis’s work. “If you would’ve told me 10 years ago that someday monkeys and humans could move stuff just by thinking about it, I would’ve laughed,” says Ron Frostig, a UC-Irvine neurobiologist. “It’s turning science fiction into science. But Dr. Nicolelis showed that it works. You cannot laugh for too long.”

Frostig is looking forward to the demonstration: “I think it will be fantastic, fantastic. You cannot argue [with] a monkey moving stuff just by thinking. It works. You can’t argue it. The same will happen with the World Cup. You will see a paralyzed man kicking a ball. How can you argue with that?”

On May 15, the two women in the study became the seventh and eighth patients to control the exoskeleton. The first woman walked “a total of 132 steps, to the awe of everyone present,” Nicolelis wrote on Facebook. He added that after walking in the exoskeleton, the second woman — the last of the participants to use it successfully — said, “When I get married, I want to borrow this exo to enter the church!”

In the final weeks, the team will have to tie up several remaining loose ends. The design for the sensory-receptor shirt still needs to be finalized and Nicolelis’s team must decide how many degrees of freedom the exoskeleton’s joints will allow. The back of the exoskeleton still needs its 3-D-printed shell, which has yet to be designed. The hoses along the legs of the device might stay exposed, Nicolelis says, because the patients think they look cool.

One thing Nicolelis knows for sure is that the final version of the exoskeleton will be controlled by a combination of thoughts and computer. “The person is going to use the EEG to decide what he wants to do, and what kind of movement he wants to select,” he explains. “And the low-level mechanics are going to be done by the exo.” The patient will generate the commands by imagining himself walking, but the exoskeleton’s computer software will robotically control the finer details, like how far back he hitches his leg to kick the ball. This shared control makes the device sturdier, and is the most practical version for these patients given their timetable.

Even with so much work left to be done in the final month before the 2014 World Cup, Nicolelis’s confidence could not be dented. “If you tell me today, if this demonstration is indoors,” he says, “I will tell you, it works.”

But the demonstration is not indoors. It’s outside, on the world’s biggest stage. There is a very real possibility that something will go wrong. Regardless, Nicolelis isn’t worried. In fact, he might be slightly delirious with enthusiasm: “Despite all of the difficulties of the project, it has already succeeded. You go to São Paulo today, or you go to Rio, people are talking about this demo more than they are talking about football, which is unbelievably impossible in Brazil.”

Before I left São Paulo, I asked Nicolelis one last question, something that the people of Brazil and his lab assistants and the patients all must be wondering, to some extent: “When do you think the exo will be completely ready?”

He laughed. “Thirty minutes before.”

Danielle Elliot (@daniellelliot) is a writer and producer based in New York. She worked on NBA TV documentaries and NBC figure skating features before making her way into the world of science writing.

Illustration by Gluekit.