Book excerpt: Mesoscopic physics refers to the physics of structures larger than a nanometer (one billionth of a meter) but smaller than a micrometer (one millionth of a meter). This size range is the stage on which the exciting new research on submicroscopic and electronic and mechanical devices is being done. This research often crosses the boundary between physics and engineering, since engineering such tiny electronic components requires a firm grasp of quantum physics. Applications for the future may include such wonders as microscopic robot surgeons that travel through the blood stream to repair clogged arteries, submicroscopic actuators and builders, and supercomputers that fit on the head of a pin. The world of the future is being planned and built by physicists, engineers, and chemists working in the microscopic realm. This book can be used as the main text in a course on mesoscopic physics or as a supplementary text in electronic devices, semiconductor devices, and condensed matter physics courses. For this new edition, the author has substantially updated and modified the material especially of chapters 3: Dephasing, 8: Noise in mesoscopic systems, and the concluding chapter 9.