While the world mourns those who died in this week's attacks in Brussels, the police are hard at work piecing together the terrorists' plot.

One thing Brussels authorities seem to have figured out, however, is the type of explosives the suicide bombers set off during the attacks.

Frederic Van Leeuw, Belgium's chief prosecutor in the case, told reporters on Wednesday that investigators found 33 pounds of homemade explosives at a house used by the two bombers who struck Brussels Airport, according to the Associated Press. Those two explosions, combined with a third in Belgium's subway, killed more than 30 people and injured at least 270.

The police also found nails — presumably to serve as shrapnel — and other raw materials for making explosive vests at the residence, according to the Chicago Tribune.

The key explosive ingredient discovered, Van Leeuw said, is a compound called triacetone triperoxide, or TATP, a crystalline powder that is a nightmare to terrorists as well as authorities.

An unstable white powder

Public domain

TATP is easy to make and hard to detect, but it is also incredibly unstable. In fact, all it takes is a firm tap to explode TATP with a force that's about 80% as strong as that of TNT. (That is why it has gained a reputation as "the Mother of Satan" among terrorists who make it, according to The Future of Things.)

The infamous "shoe bomber" used TATP in 2001, as did terrorists in London in 2005 and 2006. The chemical was also in bombs detonated at the University of Oklahoma in 2005 and Texas City, Texas, in 2006, according to explosives researchers at Northeastern University.

Before this week, it was most recently used in the November terrorist attacks in Paris.

"TATP and other explosives of the peroxide family are used extensively by terrorist organizations around the world because they are easy to prepare and very difficult to detect," Ehud Keinan, a chemist at the Technion-Israel Institute of Technology, said in a 2005 press release about his research of the chemical.

You might recognize two chemicals in TATP's full name — triacetone triperoxide — because they're ingredients you can find in your local pharmacy's cosmetics and first-aid aisles.

"TATP can be easily prepared in a basement lab using commercially available starting materials," according to GlobalSecurity.org, which also notes that "it's easy to blow yourself up when you make it."

Jimmie Oxley, an explosives researcher at the University of Rhode Island, told Tech Insider by email last year that making TATP was as easy as "baking a cake."

"We have done a lot of work trying to prevent its synthesis," wrote Oxley, who has experimented with adding trace chemicals to hydrogen peroxide in hopes of foiling TATP's homemade production. "It isn't easy to do and the ingredients are very common."

Chemistry of a nightmare

One reason TATP is difficult to detect is that it does not contain nitrogen, a key component of homemade "fertilizer" bombs that security scanners are now very good at finding.

Each molecule contains only hydrogen, oxygen, and carbon — some of the most common elements on earth — shaped in a ring.

A chemical model of triacetone triperoxide, or TATP. It's made of oxygen (red), carbon (black), and hydrogen (white). Public domain The explosive power of TATP has puzzled scientists since its discovery in 1895. Unlike nitrogen-based bomb materials, which store up energy as they're cooked into explosive form, TATP can be made at room temperature — no flames required.

So where does it get its explosive energy, if not by heating?

It wasn't until 2005 that Keinan figured out that detonating TATP was more like a massive air blast than a firebomb. When a crystal of the explosive is rattled hard enough, each solid molecule instantly breaks into four gas molecules.

"Although the gas is at room temperature, it has the same density as the solid, and four times as many molecules, so it has 200 times the pressure of the surrounding air," according to the release about Keinan and his colleagues' 2005 study of TATP.

"This enormous pressure — one-[and-a-half] tons per square inch — then pushes outward, creating an explosive force" that's on par with TNT, the release says.

"In a TATP explosion, the gas molecules give up their energy of motion to the surroundings, in the process creating the shock wave that does the damage."

Can we detect it?

Scientists are working feverishly to create practical ways to find TATP before it can be used to kill innocent people.

ACRO Security Technologies, a company founded by Keinan, has created a disposable marker-size "peroxide explosives tester," or ACRO-P.E.T.

"The ACRO-P.E.T. provides an immediate answer to whether a suspicious material that has been discovered somewhere ... contains even minute quantities of a peroxide-based explosive," Keinan told The Future of Things.

Other researchers are working on ways to find TATP when it's being transported that lack the need for a direct chemical test like that of Keinan's device.

In 2011, for example, scientists at Hitachi in Japan created a machine that sucks in air from around a passenger and — in two seconds — can sniff out minute traces of TATP.

A German research group also announced in 2015 that large amounts of TATP could be detected in transit. Because the chemical is so touchy, the group says in its study, it's usually dissolved in a special liquid before being moved around. That fluid's unique odor is what they hope security scanners of the future could sniff out.

Warning: We have purposefully omitted key details about TATP's manufacture. Do not attempt to make it or any other explosive, for that matter.