Charles Darwin is known for his groundbreaking work with the theory of evolution. His most significant contribution is the concept of natural selection, which he detailed in his seminal work, "On the Origin of Species," published in 1859. In this theory, Darwin proposed that species evolve over time through the survival and reproduction of individuals with advantageous traits, leading to the gradual adaptation of organisms to their environments. His work provided a scientific explanation for the diversity of life on Earth and laid the foundation for modern evolutionary biology. Darwin's ideas challenged traditional views and have greatly impacted various fields, including genetics and ecology.