This lecture covers the principles and equipment of Differential Interference Contrast (DIC) microscopy, explaining how it allows viewing optical path length variations and creates 3D-like images. It discusses the components of DIC equipment, such as polarizers, prisms, and analyzers, and how they interact to produce contrast images. The lecture also delves into the interpretation of DIC images, bias retardation techniques, and the comparison between DIC and phase contrast microscopy in terms of image appearance and information content.