In this article, I examine changes in the field of cognitive development and in my own thinking over the past 40 years. The review focuses on three periods. In the first, Piaget's theory was dominant, and my research and that of many others was aimed at understanding the many fascinating changes in children's thinking that Piaget documented and at correcting inaccuracies in his theory. The second period involved generating an alternative to Piaget's approach, overlapping waves theory, and specifying through microgenetic methods and computer simulations how development can be produced by variability of strategy use, adaptive choices among strategies, and discovery of new strategies. In the third period, my thinking and research, and that of many others, has increasingly focused on the interface between cognitive development and education. I close by suggesting that generating domain-specific integrated theories of cognitive development may provide a way forward for the field. [This article was published in "Child Development Perspectives," v10 n2 p128-133 Jun 2016.]