Head lice can be as small as 0.1mm when newly hatched and can grow up to 0.8mm in length (about the size of a sesame seed) . Colour - tan to dark brown in colour when they have recently fed on blood, which they do every two to three hours. When a baby louse (nymph) has hatched it is clear in colour, they are so small that it is virtually impossible to see them on the hair and scalp, or when combing out with conditioner. This is one of the reasons combing with conditioner is so time consuming. You will think there is nothing left in the hair, however they get lost in the conditioner gloop. We always recommend to use serum when combing as it is a clear liquid, kills the eggs and lice and you can see everything you have combed out. It makes for much faster results. Ensuring your family are as comfortable as possible.