1. Classical Fields and Their Associated Particles.- 2. Fermions and Bosons.- 3. Systems with Variable Particle Number.- 4. Electron Gas.- 5. Fermion Pairing and Superconductivity.- 6. Nucleon Pairing and the Structure of the Nucleus.- 7. The Superfluidity of Liquid Helium.- 8. Quantum Fields.- 9. Perturbative Methods in Field Theory.- 10. Perturbative Methods in Many-Body Problems.