Cesare Lombroso was an Italian criminologist, physician, and founder of the Italian School of Positivist Criminology. He is best known for his theories on criminal behavior, where he believed that criminals were biological throwbacks to a more primitive stage of human evolution. Lombroso's work laid the foundation for modern criminology by emphasizing the importance of scientific research and empirical evidence in understanding criminal behavior. His controversial ideas sparked debate and influenced the development of forensic psychology and criminal profiling.