Here are the stories of four young inventors who have already made their mark on the world, and one who hopes to in the years to come.

1. Chester Greenwood: Easy on the Ears

All 15-year old Chester Greenwood wanted to do was ice skate. But the bitter cold of winter in Farmington, Maine, was hard on his exposed ears. He tried covering them with gloved hands, but that made it difficult to skate. He tried wrapping a wool scarf around his head, but his ears were so sensitive to the fabric that it made him itch.

Searching for a solution, Greenwood shaped two pieces of wire into circles to cover his ears, then connected them with a longer wire to form a headband. His grandmother sewed velvet to the inside and beaver fur to the outside of the circles, to block out the winter air. His lightweight, hands-free, itch-free ear protectors became an instant hit with the other kids, who begged him to make more.

Greenwood got a patent for his “ear-mufflers” three years later in 1877, when he was just 18. By 1883, his Farmington factory produced 30,000 earmuffs a year, climbing to 400,000 by his death in 1937.

Today, earmuffs are so commonplace, it’s virtually impossible to say how many pairs are sold every year.

Greenwood became famous for earmuffs, but he wasn’t a one-hit wonder. He received numerous patents during his lifetime, including one for the metal rake we still use to collect fallen leaves every autumn. But nowhere was he as much-loved as his native Maine. To show their appreciation, in 1977, the state declared December 21st “Chester Greenwood Day,” and Farmington held its first earmuff parade, which became an annual event.

2. Louis Braille: Blind Visionary

Blind since he was three, Louis Braille received a scholarship to attend France's Institut National des Jeunes Aveugles (National Institute for Blind Children), the first-ever specialized school for the blind, when he was 10. At the time, the Institute taught its students to read by touch, tracing embossed letters on the pages of specially-made books. The letters were large so the student could differentiate them, but that also meant the books were much bigger than usual to accommodate the larger typeface. The books were very expensive to make and often became unwieldy to read, with some weighing as much as 100 pounds. As such, when Braille started school, the Institute had around 100 students, but only 14 books.

In 1821, a French soldier visited the school to introduce “sonography,” a code language read by fingertip so that soldiers could communicate at night without light or making noise. The code was made of cells that could hold 12 tiny, raised dots split into two rows of six, with the number and arrangement of dots in each cell corresponding to a particular phonetic sound. With its smaller typeface, sonography would allow the Institute to reduce the size of its books, but would also give blind students the opportunity to write for the first time with a special grid guide and embossing stylus.

After using sonography for a few years, 15-year old Braille had some ideas to make it better. The main problem was that it required multiple fingers to read because there were so many possible positions for the twelve dots to occupy. So he streamlined the code by using six dots to symbolize only letters and basic punctuation, leaving out complex phonetic sounds entirely. Students learned and read Braille's system much faster than sonography, so it quickly became the standard language at the school, and later, for blind people all over the world.

3. Philo Farnsworth: TV Star

For most farm boys, plowing the family field only inspires boredom. But for 14-year-old electronics prodigy Philo Farnsworth, going up-and-down the rows gave him the idea to project a recorded image by scanning electrons back-and-forth across a glass screen. When he consulted his high school chemistry teacher about the idea, it was so complex he had to draw a diagram on the blackboard, which the teacher promptly copied down to study later. Encouraged by his bewildered mentor, Farnsworth pursued his concept and, in 1927, at the age of 21, he developed and patented the world's first working fully-electronic television.

But like many inventions, there were other people developing related ideas at the same time. One such man, Vladimir Zworykin, had filed a patent for a similar concept in 1923, but couldn’t make it actually work. So Zworykin continued to tweak the design, resubmitting the same patent application again and again, until it was finally approved in 1933. However, due to a technicality, the original filing date read 1923, making his patent four years older than Farnsworth's.

By the time his patent was approved, Zworykin was working for Radio Corporation of America (RCA), who planned to produce televisions using his design. Believing that his 1927 patent trumped the revised 1933 patent, Farnsworth sued for royalties. Of course RCA used the technicality to claim their employee had the patent before Farnsworth, so they refused to pay him a dime.

Farnsworth had an ace up his sleeve – his chemistry teacher. The teacher testified in court and even produced the original sketch of 14-year old Farnsworth's blackboard diagram, proving he had been working on the invention well before Zworykin had even applied for his patent.

Farnsworth received a few royalty payments from RCA during television's infancy, but as America entered World War II, the government suspended production of television sets. Shortly after the ban was lifted, Farnsworth's patent expired, allowing RCA to make televisions royalty-free. This meant that, as television sales exploded in the 1950s and 60s, Farnsworth missed out on the most lucrative years of his own invention.

4. Margaret Knight: Bag Lady

As a young girl, Margaret “Mattie” Knight never played with dolls, preferring to make toys for her brothers instead. In 1849, Knight went to work in a cotton mill where she witnessed a "shuttle," a device that carries thread back and forth across a textile loom, fly off the machine when the thread broke, striking and killing a young boy about her own age.

The 12-year old Knight developed a safety mechanism that made it impossible for a shuttle to leave the loom. The design was so effective, soon virtually every new power loom carried her invention, saving countless workers from injury or death. Being so young, she didn’t bother to patent the device, so she never received royalties.

Knight wouldn't make the same mistake later in life when she invented a machine that could produce flat-bottomed paper bags. Knight had built a miniature wooden prototype in her home, but she needed a metal version to show it could hold up to the rigors of mass production. So she hired Charles Annan to make the full-sized machine for her, only to have him try to claim the patent for himself. When Knight sued, Annan's argument was that the design had to be his, because no woman could possibly understand the complex mechanics involved. Knight proved him wrong when she brought her wooden prototype to court and explained how every gear and lever worked. She won the case in 1871, making her the second woman to hold an American patent (the first was Mary Dixon Kies in 1809). Over a hundred years later, her design is still used as the basis for many modern flat-bottom bag machines.

But that wasn’t the last the world heard of Mattie Knight, “the female Edison.” During her lifetime, she was credited with about 90 inventions and received 26 patents on everything from a rotary engine to a waterproof protector for women’s skirts, becoming one of the most prolific female inventors of the 19th century.

5. Param Jaggi: One to Grow On

Even today, young inventors are working to make the world a better place. If Param Jaggi's invention, the Algae Mobile, continues on its current trajectory, it could very well become as familiar as Farnsworth's television or Greenwood's earmuffs.

Inspiration struck in 2008 when 15-year old Jaggi sat at a stop sign behind the wheel of a driver's ed car in Plano, Texas. Watching the exhaust from the car in front of him bellow up into the air, he got the idea for a small device that plugs into a muffler and can remove about 89% of the carbon dioxide from a car's exhaust. The secret: a live colony of algae that takes in the CO2 from the exhaust, uses it for photosynthesis, and then releases oxygen back into the air.

Jaggi applied for a patent in 2009 and has been continuously improving his design ever since. Over the years he's received awards at numerous competitions, including one in May 2011, when the Environmental Protection Agency recognized his sustainable design at the Intel International Science Fair, beating out 1,500 other applicants. With that kind of validation, and with a cost of only about $30 per unit, there's a good chance you'll one day have an Algae Mobile on your car. And then we'll all be able to breathe just a little bit easier.