Study of fungi, including mushrooms and yeasts. Fungi inhabit almost every niche in the environment and humans are exposed to these organisms in various fields of life. Many fungi are useful in medicine and industry. Mycological research has led to the development of such antibiotic drugs as penicillin, streptomycin, and tetracycline. Mycology also has important applications in the dairy, wine, and baking industries and in the production of dyes and inks. Medical mycology is the study of fungus organisms that cause disease in humans.