Preface to the first Edition.- Preface to the second Edition.- 1. About the Book.- 2. Historical Background.- 3. Studies of Interstellar Matter.- 4. Molecular Clouds and Cores.- 5. Concepts of Stellar Collapse.- 6. Evolution of Young Stellar Objects.- 7. Multiplicity in Star Formation.- 8. Accretion Phenomena and Magnetic Activity in YSOs.- 9. Massive Star Formation.- 10. High-energy Signatures in YSOs.- 11. Star-Forming Regions.- 12. Proto-solar Systems and the Sun.- 13. Protoplanets and Exoplanets.- A. Gas Dynamics.- B. Magnetic Fields and Plasmas.- C. Radiative Interactions with Matter.- D. Spectroscopy.- E. Abbreviations.- F. Institutes, Observatories, and Instruments.- G. Variables, Constants, and Units.- References.- Index.