Penicillium chrysogenum, coloured scanning electron micrograph (SEM). The round structures seen here are conidia, the asexual reproductive spores of the fungus. Each chain of conidia grows on a specialised hypha (stalk) known as a conidiophore. This is a common mould that is often found growing on bread. This is the species of fungus that is use to produce the antibiotic penicillin. Penicillin was the first antibiotic to be discovered. Magnification: x1250 when printed at 10 centimetres wide.