Archive footage of Sir Alexander Fleming demonstrating how he discovered the world’s first antibiotic, penicillin. Fleming discovered the Staphylococcus bacterium could not grow near the Penicillium fungus, which had contaminated his petri dish.

As an extension of the study of cells and the structure of different cells, ask students how they think penicillin is able to kill bacteria. Encourage the class to come up with a range of answers based on their understanding of what cells do and how they reproduce before explaining that penicillin interferes with the bacteria’s ability to build cell walls.