Nuclear dimorphism is a phenomenon in which cells of the body possess two types of nuclei. This most frequently occurs in the life cycles of protists, such as certain unicellular algae and protozoa. One of these nuclei is the vegetative, or trophic, nucleus, which controls somatic functions such as growth, reproduction, and cellular metabolism. The second nucleus is the generative, sexual, or reproductive nucleus, which is responsible for gamete formation. Nuclear dimorphism is often associated with sexual reproduction and is essential for the production of haploid gametes in many protist species.