Today research has come far in explaining distinct aspects of design expertise at different skill levels. However, with the increasing number of studies, we argue there is a need to assimilate present knowledge. In this paper we advance the field of design expertise by conducting a structured literature review. Through a systematic search of papers, from 1970 to today, we identify 110 papers concerning design expertise. We then analyze the accumulated research, and map how design expertise research has evolved, in terms of what we know and what remains unexplored. Through the review, we contribute with a distinction of skills acquisition at increasing levels of design expertise.