Optical response in magnetic media depends on their magnetic state, and this dependence manifests itself in magnetooptic (MO) effects. This chapter provides a brief overview of magnetooptics in magnetic materials. It deals with the bases of magnetooptics from the phenomenological viewpoint of classical wave optics and discusses the MO effects in multilayers. Magnetooptic techniques with highly coherent monochromatic radiation provide a sensitive, nondestructive, noninvasive, and noncontact tool in the metrology of magnetic multilayers and nanostructures. The concept of a memory with thermomagnetic recording and MO sensing of recorded information using nonmechanical access was proposed in 1965. To understand the origin of magnetooptic effects on a phenomenological basis, it is not necessary to go into details of microscopic models describing the response of magnetic media to electromagnetic plane waves. Several kinds of materials were considered as magnetooptic recording films before the magnetooptic memories become commercially available.