Paul Anastas, the Yale chemist often credited as a founder of green chemistry, opens this module by laying out what the field actually means. He walks through the twelve principles of green chemistry, the framework he co-developed for designing chemical processes that reduce or eliminate hazardous substances rather than cleaning them up afterward. Anastas argues that green chemistry is not a compliance add-on but a redesign of how molecules and reactions are chosen in the first place, with implications for energy use, waste, and raw materials across industries. The talk sets up the rest of the course by connecting these principles to broader sustainability goals, framing chemistry as a lever for systemic change rather than incremental fixes. It is a short, focused introduction meant to establish vocabulary and motivation before the course moves into technical detail.