Rydberg atoms were the focus of much of Keith MacAdam's scientific life. Why he found them so fascinating becomes obvious with a brief summary of their properties. Their properties are exaggerated compared to normal atoms, allowing the introduction of novel detection techniques and clear manifestiations of unexpected physical phenomena. Keith was one of the pioneers in the study of Rydberg atoms. His background in radio frequency resonance spectroscopy was the perfect preparation for his initial Rydberg atom work, high resolution microwave spectroscopy, and his measurements are still the best. He is best known, though, for his beautiful work on  collisions of charged particles with Rydberg atoms, particularly charge exchange, the process in which the Rydberg electron hops from its initial ion core to the incoming ion. In spite of the fact that the "modern" Rydberg atom experiments began forty years ago, Rydberg atoms, today at microKelvin temperatures, remain a subject of intense interest.