Alexander Fleming is credited with the discovery of penicillin in 1928. While conducting research on influenza, he noticed that a mold, later identified as Penicillium notatum, had contaminated one of his petri dishes and killed the surrounding bacteria. This serendipitous observation led to the development of penicillin as the first antibiotic, revolutionizing medicine by providing a powerful treatment for bacterial infections. Penicillin dramatically reduced mortality rates from infections and has since saved millions of lives, establishing the foundation for the field of antibiotics and influencing public health worldwide.