Paul Anastas, the Yale chemist often credited as a founder of green chemistry, opens this module by laying out what the field actually means and why it matters. He walks through the core idea that chemistry can be redesigned from the molecular level up to eliminate hazardous substances and waste rather than clean them up afterward, tying this directly to his twelve principles of green chemistry. Anastas argues that this reframing is not a minor efficiency fix but a route to fundamentally rethinking how products, processes, and materials are made, with sustainability as the design goal rather than an afterthought. As the opening module of his Yale course, it sets up the vocabulary and framework the rest of the series builds on.