What is the life cycle of a lice?

The life cycle for Head lice is fairly simple -

Egg -> Nymph -> Adult

Nits, or lice eggs, hatch in about a week. Baby lice or nymphs are about the size of a pinhead when they hatch, and quickly mature into adult lice in about a week. Adult lice can then live for about 30 days, with females laying up to 8 nits a day, repeating the cycle.

Reproduced from the Centers for Disease Control and Prevention.