Lynn Margulis (1938-2011) was an American biologist renowned for her groundbreaking work in evolutionary theory. She is best known for her theory of symbiogenesis, which proposed that the development of complex cells was driven by symbiotic relationships between simpler organisms. Margulis's research revolutionized our understanding of how life evolved on Earth, earning her numerous accolades including the National Medal of Science. Through her work, she left a lasting impact on the fields of biology and evolution.