Head lice develop in three stages: nit, nymph, and adult louse. The adult female louse lays about six to ten eggs each day. Nits are the oval-shaped lice eggs that the female louse lays. Nits can be lighter or darker shades of brown or gray in color, and they are cemented to the hair shaft. Nits hatch into a nymph or baby louse within one week. A week later, the nymph becomes an adult louse.