Work on cognitive expertise has defined a new approach by describing the superiority of experts over novices as a perceptual advantage. By extending this line of research, many authors have developed theoretical proposals aimed at defining the influence of prior knowledge on the perceptual processes implemented by experts (Gobet & Simon, 1996a, 1996b). The main objective of the experimental research presented here was to show how the interaction between knowledge and the perceptual processes of experts constitutes a foundation for the expression of expertise. We will first present a summary of the main results highlighting the richness of the repertoire of expert knowledge, as well as the process of perceptual categorization which seems to be a product of the athlete's activity. In addition, we revealed the perceptual sensitivity of the experts to prototypical configurations.