The condition of having two sets of chromosomes (and therefore two sets of the genes carried on them) is called diploidy. Organisms having only one set of chromosomes are described as haploid.

Diploidy is important in reproduction. An adult individual has two sets of chromosomes. Its gametes (eggs in the female, sperm or pollen in the male) have only one set: a human egg, for example, has only 23 chromosomes before it is fertilized. Gametes are said to be haploid. They are formed by a special kind of cell division, called meiosis.

In some species, such as yeast and fungi, organisms are permanently haploid. Most familiar, non-microscopic species are diploid.

The image is of a diploid genome arranged in chromosomes.