Ilya Ilyich Mechnikov was a famous Russian embryologist, bacteriologist and immunologist born in 1845. He discovered phagocytosis in 1882 and developed the phagocytic theory of immunity. Mechnikov received the 1908 Nobel Prize in Medicine for his work on phagocytosis. He made important contributions to the fields of microbiology, immunology and pathology that helped other scientists develop treatments for diseases and improved societal understanding of these subjects.