Book excerpt: The 18th Advanced ICFA Beam Dynamics Workshop on ''Quantum Aspects of Beam Physics'' was held from October 15 to 20, 2000, in Capri, Italy. This was the second workshop under the same title. The first one was held in Monterey, California, in January, 1998. Following the footstep of the first meeting, the second one in Capri was again a tremendous success, both scientifically and socially. About 70 colleagues from astrophysics, atomic physics, beam physics, condensed matter physics, particle physics, and general relativity gathered to update and further explore the topics covered in the Monterey workshop. Namely, the following topics were actively discussed: (1) Quantum Fluctuations in Beam Dynamics; (2) Photon-Electron Interaction in Beam handling; (3) Physics of Condensed Beams; (4) Beam Phenomena under Strong Fields; (5) Quantum Methodologies in Beam Physics. In addition, there was a newly introduced subject on Astro-Beam Physics and Laboratory Astrophysics.