In this seminar I’ll tell the story of cavity quantum electrodynamics (cQED) from first principles, building towards a new type of sub-micron waist resonator recently developed in the Simon/Schuster collaboration at Stanford. We will start by developing physical intuition for cooperativity, the figure of merit that controls performance of light/matter coupled systems including photon collection efficiency, cavity-mediated information exchange fidelity, and even coherence of interactions of photonic quasi-particle. Maximizing cooperativity will push us in either of two directions; (1) high finesses or (2) small mode waists. The high-finesse route is well explored by many leaders in the field of cQED, so I will emphasize the quest to small mode waist resonators, motivating near-concentric resonators, bow-tie resonators, and finally, our lens cavities. These lens cavities sport mode waists below a micron, entering the strong coupling regime at finesses well below 100. I’ll share preliminary data demonstrating single-atom coupling to such a cavity, and a test-bench demonstration of an array of small waist cavities that we intend to integrate with an atom array.