Conventional stereoscopic three-dimensional displays suffer from vergence- accommodation conflict because the stimulus to accommodation is fixed by the display panel and viewing optics, but that to vergence changes with image contents. With the recent rapid development of head-mounted displays, several methods have been proposed to offer the accommodation cues, among which multifocal display technology is an effective and practical solution. The first two decades of this century has witnessed the fast growth of multifocal displays from basic concept to mature implementations. This review systematically presents the state-of-the-art multifocal display design and development. Firstly, a comprehensive classification of numerous potential optical architectures to provide the multiplanar functionality is introduced, based on how the information is multiplexed and how the focal planes are generated. Next, the strengths and obstacles of reported or potential designs in each category are analyzed and compared with each other. In addition to enabling optics, the image rendering approaches for the multifocal planes are also described. This review presents a sufficient collection of past designs and is expected to offer a roadmap for future research and development of multifocal displays.