This paper provides a tutorial on the principles of holography, followed by a review of a newly developed 3-D imaging technique in which 3-D optical information of an object can be extracted by a 2-D optical scan of the object. The technique is called optical scanning holography (OSH). In the context of optical scanning holography, we discuss some of its potential applications such as holographic information transmission and television (TV) system, 3-D image coding and decoding, 3-D microscopy, and 3-D optical remote sensing. In most cases, feasibility has been proven but awaits broader application.