Light-field optics is used in light-field cameras to alter the focus condition of an image after it is obtained. This unique function implies that information captured with a light-field camera is not a “picture”; rather, it is a real object image. Thus, a two-dimensional (2-D) image of any focus condition can be generated from the acquired data. An explanation is provided on how a light-field camera records or encodes a three-dimensional (3-D) scene onto a 2-D plane as light-field data, and how the data are decoded back into a 3-D image with a light-field display. Other unique applications based on light-field optics are discussed. Unlike conventional optical systems, light-field optics does not require optical conjugation between the display plane and image plane. Thus, light-field optics can provide an effective means of advancement for conventional optical instruments. To demonstrate the potential applications of light-field optics, we developed a light-field camera and display.