Our Galaxy, Host of the Interstellar Medium -- Radiations and Magnetic Fields -- Radiative Transfer and Excitation -- The Neutral Interstellar Gas -- The Ionized Interstellar Gas -- The Interstellar Medium at High Energies -- Interstellar Dust -- Heating and Cooling of the Interstellar Gas -- Interstellar Chemistry -- Photodissociation Regions -- Shocks -- Shock Applications -- Interstellar Turbulence -- Equilibrium, Collapse and Star Formation -- Changes of State and Transformations