The main purpose of the book is to present a description of the mechanism of high-temperature superconductivity and to discuss the physics of high-temperature superconductors, both entirely based on experimental facts. The pairing mechanism of this remarkable phenomenon is based on an anomaly found in tunneling (V) characteristics of some cuprates. By using the soliton theory, it is then shown that this anomaly is caused by pairs of quasi-one dimensional excitations - bisolitons - bound due to a moderately strong, nonlinear electron-phonon interaction. At the same time, analysis of experimental data unambiguously shows that magnetic (spin) fluctuations mediate the phase coherence in cuprates. The mechanism of superconductivity in quasi-one dimensional organic superconductors and heavy fermions is discussed too. In cuprates, the origins of five different energy/temperature scales are identified. Finally, three main principles of superconductivity are introduced at the end of the book. Analysis of tunneling and angle-resolved photoemission measurements is presented in the last chapter. The book which contains 300 pages with 180 illustrations is addressed to researchers and graduate students in all branches of exact sciences.