Random inhomogeneous media may possess unique physical properties that are significantly enhanced and may attain a level of practical importance and versatility that rivals or surpasses their geometrically ordered counterparts. Making judicious use of these enhancement effects, as well as of other aspects of the many complex resonances that distinguish these systems, can lead to new and unexpected physics and many applications. Localization of various sorts of optical excitations occur and recur in a wide gamut of disordered systems, leading to the enhancement of many optical phenomena,...