Elie Metchnikoff was a Russian biologist best known for his pioneering work in immunology. Born in 1845, he discovered the process of phagocytosis, where certain cells in the body engulf and destroy harmful pathogens. This groundbreaking research laid the foundation for understanding how the immune system protects against infections. Metchnikoff's contributions earned him the Nobel Prize in Physiology or Medicine in 1908, which he shared with Paul Ehrlich. He also studied the health benefits of fermented foods, particularly yogurt, believing they could enhance immunity and promote longevity. His work has had a lasting impact on both medicine and microbiology.