1. Cognitive enhancers; such as, mind drugs.
2. Popularly referred to as "smart drugs," they are substances which boost human cognitive abilities (the functions and capacities of the brain).

Typically, nootropics work by increasing the brain's supply of neurochemicals (neurotransmitters, enzymes, and hormones), by improving the brain's oxygen supply, or by stimulating nerve growth.

With a few notable exceptions, nootropics have very low or no toxicity, making overdose unlikely. Most have few or no side effects, and many nootropics potentiate each other.