George Sudarshan was an eclectic thinker, and one of the most profound physicists of the last century. We review here a small part of his oeuvre, focusing on his pioneering contributions to the quantum Zeno effect, quantum channels (the Kraus-Sudarshan representation) and quantum semigroups (the Gorini-Kossakowski-Lindblad-Sudarshan equation). These topics are of crucial importance in the booming field of quantum mechanics and applications.