The white half moon on nails is called the lunula, which is a part of the nail matrix located near the base of the nail. The lunula is a whitish color and takes up a small portion of the bottom of the nail. It is usually most visible on the thumb. The lunula is where living cells transform into non-living keratinized nail cells, contributing to the overall health and appearance of nails. The absence of a visible lunula may indicate that it is hiding under the skin called the proximal nail fed, which is a delicate area of the nail and easily damaged. The appearance of the lunula can also indicate nail health, as strong, white moons at the base of each nail indicate strong “Qi” or “fire”. However, changes to the lunulas appearance could be a cause for concern and should be reported to a doctor. The materials or ingredients of the lunula are not applicable as it is a natural part of the nail.