Richard Mohaupt, age 11 for his questions:

What is penicillin

In 1928, a stray mold landed on a soupy culture of germs in a London laboratory. As it thrived, it produced a chemical which killed many of the disease germs. But it did not harm living body cells. The mold was a member of the fungus genus Penicillum. The broth in which it grew and produced its germ killing chemical became the first of the modern wonder drugs.

Later, chemists discovered how to separate the germ killing chemical from the broth or culture in which the penicillin molds had grown. This chemical is the wonder drug we call penicillin.