Clanestine chemistry generally refers to chemistry carried out in illegal drug laboratories (known colloquially as labs), but can include any kind of secretive laboratory operation. It is important to distinguish between large- and small-scale clandestine laboratories. Larger labs are usually run by gangs or organized crime with the intention of production for distribution on the black market. Smaller labs are usually run by individual chemists working clandestinely in order to synthesize smaller amounts of controlled substances, often because of the difficulty ascertaining the purity of other, illegally synthesized drugs obtained on the black market. The term "clandestine lab" is generally used in any situation involving the production of illicit compounds, regardless of whether the facilities being used qualify as a true laboratory.