The purpose of this chapter is to explain the various ways to account for the capability to perceive form. The chapter includes a description of the notion of contours and a review of the factors influencing the perception of it. Then the fundamental physiological process called lateral inhibition is described. This process helps in understanding perceptual phenomena like the Mach bands. Another way of approaching form perception, the Gestalt approach, is then described, which includes the figure/ground distinction and the principles of perceptual grouping like similarity, continuity, and good continuation. Then, the theory of multiple spatial channels, which is based on the notion of spatial frequency, is presented. This notion refers to the number of cycles (periods alternating between light luminance and dark luminance) per degree of visual angle. This theory leads to the contrast sensitivity function, which describes the link between the spatial frequency and the perception threshold. Finally, perceiving a form requires to recognizing it; the chapter also addresses this form recognition issue, describing the main approaches and models in the field.