This picture shows the three stages of the head lice life cycle, including the egg or nit, nymph, and adult louse, as compared to the size of a penny for scale.
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.
