An overview is presented of the history of retroreflection including biological and man made retroreflection and the evolution of the technology of the latter. Emphasis is on the optical characteristics of retroreflecting devices with the strongest emphasis on corner cube retroreflectors. A comparison of various corner cube and spherical retroreflector designs is given. Optical characteristics include return beam intensity, beam shape, beam polarization, effects from aperture sizes, materials and source properties such as coherent and incoherent light sources. The performance of retroreflectors having macroscopic vs. nanoscopic (wavelength scale) configurations and designed in error is discussed. Emphasis is on the performance properties of solid, open, full and partial corner cube retroreflectors made with various materials and coatings. An over view of a few applications for use of retroreflectors in today's counter terrorism and crime fighting world are discussed.