How children learn to retrieve answers to basic (single-digit) addition problems and how teachers can support children's learning of retrieval has captivated my attention as a researcher and teacher educator for the last 25 years. In this chapter, I describe this research and explain how I got started with the help of Professor Mike Lawson. I then present findings from a series of microgenetic studies to illustrate the different effects problem-solving practice has on children's development of retrieval.