Carbon-, boron- and silicon based materials have recently found a renaissance due to the possibility to incredibly diversify their crystal structures and compositions under high pressure. The book describe the last-decade experience of the author in high-pressure synthesis of such materials and is focused on the promising methodological approaches to expand the domains of possible materials for new applications. The book presents the "high pressure" materials from the thermodynamic and alternative points of view, and discuss possible mechanisms of their formation. The formalized description of both "design" and recent advances in high pressure synthesis is given. After that, principal directions of modern high-pressure materials design are described, i.e. (i) advanced superhard materials - boron-rich solids, and (ii) new axis - recently proposed by the author and its collaborators - optoelectronic silicon materials that cover a wide range of possible applications. The book may beinteresting to materials scientists of diverse fields, i.e. physicists and chemists working with high pressure, superhard and photovoltaic materials, as well as to carbon, boron, and silicon communities.