When did Alexander Fleming work?

Alexander Fleming worked primarily in the early to mid-20th century. He is best known for his discovery of penicillin in 1928, which revolutionized medicine and antimicrobial treatment. Fleming continued his research and contributions to microbiology throughout the 1930s and 1940s, particularly during World War II. He received the Nobel Prize in Physiology or Medicine in 1945, alongside Howard Florey and Ernst Boris Chain, for their work on penicillin.