Dimorphic fungi are a type of fungus that can exist in two different forms: as yeast or as mold. This ability to switch forms is often influenced by environmental conditions, such as temperature and nutrient availability. In their yeast form, they are typically unicellular, while in their mold form, they grow as multicellular filaments called hyphae. These fungi are significant in medicine and ecology. Some dimorphic fungi, like Histoplasma capsulatum and Coccidioides immitis, can cause diseases in humans, particularly in immunocompromised individuals. Understanding their life cycle and forms is crucial for developing treatments and managing infections.