Nearly all fungi form and release vast quantities of spores as part of their life cycle. Spores are the main reproductive units for fungi and are usually single cells. They may be produced either directly by asexual methods or indirectly by sexual reproduction. Spores are commonly formed by the fragmentation of the mycelium or within specialized structures (sporangia, gametangia, sporophores, etc.). Some spores, especially those of primitive fungi, have flagella and can swim, though most are nonmotile. When a spore lands in a suitable location, it germinates and grows to form a new fungal individual.