A person's chronotype changes with age; babies are Lions, toddlers are Bears, adolescents become Wolves, and then it sets into one of the three or four types around age 23-24 for 25-30 years.

People have a genetic sleep code called their chronotype, which dictates when their brain releases hormones like melatonin, cortisol, adrenaline, and dopamine.

There are three known chronotypes, but Dr. Michael Breus is famous for discovering a fourth one.

Chronotypes, such as early bird or night owl, are genetic and determined by the PER3 area on a person's genome.