Lice are tiny parasitic insects that live on humans, primarily on the head. Here is what lice look like in their various stages:

• Adult lice are about 2–3 millimeters long, roughly the size of a sesame seed or a poppyseed. They are grayish-white, tan, or sometimes reddish-brown in color, depending on when they last ate. They have six legs with claws adapted for gripping hair strands. Adults crawl and do not jump or fly.
• Nymphs are juvenile lice that look like smaller versions of adults, about the size of a pinhead. They take about a week to mature.
• Eggs (nits) are tiny ovals about the size of a knot in thread, usually white or yellowish, and they stick firmly to the hair shaft near the scalp. Nits can be mistaken for dandruff but are harder to remove as they are glued to the hair.

Lice can vary in color to blend in with hair, appearing darker or lighter depending on hair color. They move quickly and are most often found close to the scalp, behind ears, and near the nape of the neck. Adult lice feed on blood and cause itching due to their bites. People with lice often notice itching, a tickling sensation from something moving in the hair, difficulty sleeping, and sometimes sores from scratching the scalp. In summary, lice look like small insects about the size of a sesame seed with a gray, tan, or sometimes reddish appearance, six legs with claws, and eggs that appear as small white or yellow oval shapes firmly attached to hair near the scalp. A magnifying glass or good lighting may be needed to see them clearly. This description applies to head lice, the most common type found on humans.