In 2016, we reported the first Ni-based metallaphotoredox C-S cross-coupling reaction involving thiyl radicals (Figure ). Although it was known that thiols can be readily oxidized to thiyl radicals by a suitable photocatalyst, metalcatalyzed cross-coupling of thiyl radicals with aryl halides was elusive. We reasoned that engaging thiyl radicals in C-S cross-coupling with aryl halides could solve several problems including catalyst deactivation by thiolate anions, poor functional group tolerance, the need for specialized ligands, and harsh reaction conditions. Therefore, we developed an operationally simple metallaphotoredox C-S methodology. The coupling reaction is air tolerant with a broad scope allowing for the formation of a wide variety of thioethers in high efficiency and remarkable chemoselectivity. This work, uniquely enabled by photoredox catalysis, also represents the first example of heteroatom radicals engaging with a transition metal cross-coupling catalyst. Distinct from previously reported metallaphotoredox cross-couplings, a Ni(0) intermediate is not involved in this C-S cross-coupling, and the reaction is mediated by Ni(I)-species. Since the reaction is reliant on the use of a coordinating pyridine base, we postulated that the base may be stabilizing the coordinatively unsaturated Ni(I)X and/or Ni(I)-sulfide species, especially allowing the former to engage thiyl radicals. We proposed that visible light excitation of the Ir(III) photocatalyst generates a long-lived, and highly oxidizing triplet state *Ir(III) complex (E1/2 = +1.21 V vs. SCE). Single-electron oxidation of the thiol (E1/2 = +0.83 V vs. SCE for benzyl thiol) by the photoexcited *Ir(III) complex produces a thiol radical cation with the concomitant formation of an Ir(II) complex. In the presence of a weak base, the thiol radical cation generates thiyl radicals that are trapped by Ni(I)X species to generate a Ni(II)SR(X) complex, which can be reduced to a Ni(I)SR complex by the Ir(II) photocatalyst with concomitant regeneration of the Ir(III) photocatalyst. The Ni(I)SR complex can then undergo oxidative addition into an aryl iodide to form a Ni(III)SR(X)Ar complex, which upon reductive elimination delivers the desired thioether product and a Ni(I)X species. This proposed mechanism has since been vali-dated by several groups and invoked in other C-heteroatom cross-coupling reactions. In 2019, Pan disclosed an electrochemical version of the Ni-catalyzed C-S cross-coupling reaction (Figure ). Using an undivided cell and constant potential conditions, a wide variety of alkyl/aryl thiols were coupled with aryl iodides. Like the photochemical conditions, the electrochemical method requires the use of a coordinating pyridine base. This report shows similar scope to ours owing to the mechanistic similarities between homogenous photocatalysis and paired electrolysis. The mechanism proposed for the electrochemical C-S cross-coupling is depicted in Figure . While these pioneering photochemical and electrochemical C-S crosscoupling methods were limited to aryl iodides, other groups have extended these methodologies to encompass aryl bromides and chlorides.