The chapter is organised into two main sections. The first one discusses how research on general characteristics of expertise informed our understanding of student learning. We summarize the key findings of expertise research in cognitive psychology over the last 30 years, along with the main explanations that have been suggested for these findings. We also indicate the main implications for teaching and learning. After a critique of a purely cognitivist account of expertise, we move to the next section in which we discuss expertise in teaching. We show how some ideas from classical expertise research have been applied for understanding teacher expertise and, simultaneously, how these ideas were enriched with other views of expertise. In the final section, we briefly turn to some emerging areas of expertise research that are particularly pertinent to the learning sciences.