The past century has yielded a plethora of advancements in the science of learning, from expansions in the theoretical frames that undergird education research to cultural and contextual considerations in educational practice. The overarching purpose of this chapter is to explore and document the growth and development of the science of learning using a tripartite approach. The authors first provide an overview of definitions of learning that have been forwarded in the extant literature, with particular emphasis on journals published by the American Educational Research Association. Next, they overview the epistemic frames that have undergirded investigations of learning during the past century. Finally, they explore the ways in which the nature of investigations of learning has transitioned over time and how these transitions have manifested themselves in settings such as classrooms. In reflecting on the maturation and adaptation of the science of learning over the past century, the authors conclude with thoughts on the future of the science of learning.