In a healthy individual, one can always find the half-moon shape at the bottom of the nail. It is a part of the matrix and reveals a lot about your health. Missing half-moon in some cases can be due to malnutrition, depression or anemia.

Lunulae that have a blueish tint could suggest Wilson's disease, a rare inherited genetic disorder in which copper accumulates in the liver, brain and other organs. Red lunulae may indicate heart failure, research shows.

What deficiency causes black lines on nails? Deficiencies in vitamin B12, vitamin D, and protein can cause dark lines in nails. Other causes can include cancer, too much iron, and other health conditions.

A manicure in which the moon, or lunula, is painted a contrasting color to the rest of the nail or simply left bare. The original moon manicure was worn by screen stars back in the '20s.