Starting with the pioneering work by the Kochi in 1962 and 1974, it was established that Cu(II) and Cu(I)salts could independently serve as photosensitizers to mediate chlorination and cycloaddition reactions respectively. However, McMillin and co-workers demonstrated Cu(I)-bis-phenanthrolines as complexes having low metal-to-ligand charge transfer (MLCT) states that can be leveraged for photocatalysis. Sequential studies by Kutal, Mitani, and Sauvage 53 groups showcased the potential of copper(I) complexes for the photocatalysis of organic transformations. A distinguishing feature of the tetra-coordinated copper (I) complexes, as opposed to the hexa-coordinated Ru(II)/Ir(III) complexes, is their ability not only to promote electron transfer and energy transfer processes to generate high energy radical species but also, to capture radical or anionic species, providing access to unique mechanistic pathways enabling cross-coupling reactions. Moreover, exploiting the versatility of copper complexes in undergoing MLCT, LMCT, ILCT, and LLCT excitations provides innovative routes to trigger new reactivity and utilize solar energy to propel chemical reactions.