The type of organism used to create antibiotics like penicillin is a fungus, specifically a strain of the mold *Penicillium chrysogenum*. Fungi produce these antibiotics as a defense mechanism against bacteria in their natural environments. The discovery of penicillin in the early 20th century revolutionized medicine by providing an effective treatment against bacterial infections. This has paved the way for the development of numerous other antibiotic medications derived from different fungal and bacterial sources, significantly improving healthcare and increasing life expectancy.