Penicillium is a genus of ascomycetous fungi of major importance in the natural environment as well as food and drug production. Members of the genus produce penicillin, a molecule that is used as an antibiotic, which kills or stops the growth of certain kinds of bacteria inside the body.
This Scanning Electron Micrograph (SEM) of Penicillium showing the spores in basipetal succession (youngest spore at the base) forming chains from the flask-shaped phialides (conidiogenous cells).