Urie Bronfenbrenner is almost certainly best known for his theoretical writings about the ecology of human development. His interest in theory was not, however, separate from his practical concerns, particularly those related to early education and care of children and the families and teachers who interact with them. From the role that he played in the development of Head Start in the United States to his final publications, we show that his theory, as it developed over the course of three phases, was both influenced by and an influencer of his practical concerns.