Since its discovery in cosmic rays, the muon has played an important role in our understanding of nature. Muons are fundamental subatomic particle 207 times heavier than an electron. Accelerators and cosmic-ray collisions produce muons, but the particles quickly decay. That makes muons rare in nature. Muons possess a quantum mechanical property called spin, analogous to the twirling of a top. Because of this trait, muons behave like tiny bar magnets. Their spin also makes them into minute gyroscopes, responding to upward or downward forces by swinging the axes of spin around horizontally. The muon provides a rich variety of applications in diverse areas of science, including condensed matter physics and chemistry. High energy physicists are seriously considering the design and construction of a muon collider. Negatively misbehaving muons bolster earlier evidence of new physics beyond the standard model. Important international leading-edge research results are presented in this volume.