In this account, we describe how some organic diselenides were successfully used in the past as reagents for asymmetric stereoselective synthesis and more recently as precursors of catalysts and reagents applied in new green protocols. A biomimetic approach offered the possibility to perform oxidative reactions using hydrogen peroxide as oxidant and water as medium affording the desired products in excellent yields under mild conditions. The umpolung of the selenium atom gave novel nucleophilic reagents having a strongly accelerated reaction rate in on water conditions. Finally, the use of diselenides to exploit specific biological activities is described here as seminal examples of a promising field of research currently under investigation in our group.