Did you know that head lice are tiny engineers? They don't just lay eggs anywhere—they lay them for survival. ​The Incubation Rule: Lice lay their newest eggs (nits) less than 1/4 inch from the scalp. Why? Because they need the consistent warmth of your head to incubate and hatch. Without that body heat, the egg won't survive. ​The "Timeline" Effect: As your hair grows (about 1/2 inch per month), that "old" egg moves further away from the scalp. This creates "open real estate" closer to the skin