Penicillin is a powerful medicine that kills bacteria and fights infections. Discovered accidentally in 1928 by scientist Alexander Fleming, penicillin became the world's first antibiotic, a medicine that stops bacteria from growing and multiplying inside your body.

Before penicillin, a simple cut could turn deadly if bacteria infected the wound. Illnesses like pneumonia and strep throat often killed people because doctors had no way to fight the bacteria causing them. Fleming noticed that a type of mold (similar to what grows on old bread) produced a substance that killed bacteria in his laboratory. Scientists eventually figured out how to make this substance into a medicine.

During World War II, penicillin saved countless soldiers' lives by preventing infected wounds from becoming fatal. Today, doctors prescribe penicillin and related antibiotics for ear infections, strep throat, and many other bacterial illnesses. When you take penicillin, it attacks the walls of bacterial cells, causing them to break apart and die.

Some people are allergic to penicillin, so doctors always check for allergies before prescribing it. The discovery of penicillin revolutionized medicine and launched the age of antibiotics, turning many once-deadly diseases into treatable conditions. Fleming won the Nobel Prize for his discovery, which has saved hundreds of millions of lives.