The review papers in this volume provide an in-depth examination of complex astrophysical phenomena of star formation via multi-wavelength observations and modeling. Among the fundamental issues discussed in the book are: • The role of gravity and magnetized turbulence in the formation and evolution of molecular clouds • The stellar feedback (supernovae, HII regions, winds, cosmic rays) in regulating star formation • The origin of the stellar initial mass function and its universality across various environments • Jets, magnetic fields and high energy particles in stellar clusters • The origin of the first stars and black holes The goal of these papers is to review the major processes governing star formation and to investigate how they are interlinked. In doing so, they provide an in-depth look at the tremendous theoretical and observational progress that has been made in the recent past and also outline future perspectives. Previously published in Space Science Reviews in the Topical Collection "Star Formation”