Clandestine chemistry

secret, illegal production of chemical products such as drugs and explosives

Clandestine chemistry is chemistry that occurs in a lab that is used for making illegal drugs, usually using unsafe equipment. The use of this unsafe laboratory equipment will sometimes result in explosions, fires or heavy flows of noxious fumes. Meth labs are the main form of clandestine laboratories and are used for making methamphetamine (Crystal Meth), a kind of illegal drug. "Clandestine" means "secret".

Moonshiner by Finnish painter Joseph Alanen (1916)
An impure tablet sold as MDMA seized by law enforcement in the United States. The tablet contained no MDMA; instead, it contained a mixture of BZP, methamphetamine, and caffeine.