Introduction. Stimulated emission: could the laser have been built more than 50 years ago?: Stimulated emission. The role of stimulated emission in the theory of light dispersion. Experimental proofs of negative dispersion. More on negative absorption. Notes. Intermezzo: Magnetic resonance and optical pumping: Introduction. Magnetic resonance.

Bloch, Purcell and Zavoisky. Bloch equations. Experimental proofs of population inversion. The concept of negative temperature. The Overhauser effect. Spin echo. Optical pumping. The maser: introduction.

Weber's maser. Townes and the first ammonia maser. Basov and Prokhorov and the Soviet approach to the maser. The three-level solid-state maser. Optically pumped masers. Maser action in nature. Other proposed systems. The laser: Introduction.

The Townes and Schawlow proposal. Townes' and Schawlow's ideas. The Gordon Gould story. The Dicke coherence-brightened laser. Soviet research. Notes. The Laser: Further progress: Introduction. The ruby laser.

The four-level laser. The gas laser. Laser cavities. Further progress in the gaseous laser. The liquid laser: Dye and chelate lasers. The chemical laser. The semiconductor laser. The free-electron laser.

The statistical properties of light: Introduction. The introduction of the concept of the photon. Fluctuations of radiant energy. Bose and the statistics of radiation. Further developments in the theory of fluctuations of radiation field. The Hanbury Brown and Twiss experiment. The quantum theory of coherence. The discussion of the need for quantum optics.

Experimental studies of the statistical properties of light. Notes. Subject and Author indexes.