Three forms of lice
Three forms of head lice exist: nits, nymphs, and mature adults.
Nits are lice eggs that attach to the hair shaft and usually hatch within a week.
The microscopic eggs are easy to mistake for dandruff or residue from hair styling products.
Once the eggs hatch, lice are known as nymphs, an immature form of the parasite that is grayish tan in color.
After nine to 12 days the nymphs mature into adults, the average size of which is roughly 2–3 millimeters, or about the size of a sesame seed