Microsporidia are a group of tiny, spore-forming parasites that primarily infect the cells of animals, including humans. They belong to the kingdom Fungi and are known for their simple structure, lacking many of the organelles found in other eukaryotic cells. These organisms can cause infections, particularly in individuals with weakened immune systems, such as those with HIV/AIDS. The life cycle of Microsporidia involves both a spore stage and a vegetative stage. Once ingested or introduced into a host, the spores germinate and invade host cells, leading to various health issues. Common symptoms of microsporidiosis, the disease caused by these parasites, include diarrhea and weight loss.