A mycelium is the network of thread-like hyphae of a fungus. Fungus reproduce by creating spores either sexually or asexually. The nuclei in fungal hyphae are haploid except for diploid stages formed during sexual reproduction. Sexual reproduction in fungi commences when hyphae from two genetically different mycelia release pheromones that bond to receptors on the surface of each other. In some nuclei the haploid nuclei pair up two to a cell, one from each parent. This mycelium is coined "dikaryotic" meaning 2 nuclei. The haploid nuclei contributed by each of the two parents fuse producing diploid cells. These diploid cells then undergo meiosis to produce haploid cells which in turn turn into spores that disperse and create new mycelia. This type of reproduction provides genetic variation.