Condensed Matter Physics is the most active research field in present-day physics; both in the number of researchers engaged in its pursuit and in the volume of publications and funded projects generated by their activities. Liquids, solids and gases were the condensed phases of matter usually studied during the nineteenth century and the earlier decades of the twentieth. The study of the solid phase overlapped with that of other well-entrenched research fields such as crystallography, and with the ongoing investigations of the properties of materials (e.g. tensile strength, the magnetic and elastic behavior of solids, etc.) in relation to the transformations they undergo under different regimes of temperatures, pressures, and other variables. In the second half of the century these researches, under the rubric of solid-state physics, were expanded to include the investigation of semiconductors and of exotic phenomena first encountered at very low temperatures, such as superconductivity. The incorporation of concepts and methods from other areas of physics, especially quantum mechanics, together with the study of phase transitions and critical phenomena, led to widening the field to liquids and other phases of matter. Consequently the name of the discipline was changed to condensed matter physics. The applications of this branch of physics are at the basis of most of the revolutionary technological innovations that have deeply transformed human existence in the last few decades. These include the role of semiconductors in the rapid development of novel forms of telecommunication, the development of computer systems and their multitudinous applications, medical diagnostic and surgical devices, new observational and experimental instruments that extend the reach of various scientific disciplines, and many other applications.