1. Classical Approach -- 1.1 Introduction -- 1.2 Landau Theory -- 1.3 Broken Symmetry and Condensation -- 1.4 Ergodicity -- 1.5 Gaussian Approximation -- 1.6 The Ginzburg Criterion -- 1.7 The Scaling Hypothesis -- 2 The Ginzburg-Landau Functional -- 2.1 Introduction -- 2.2 Classical Systems -- 2.3 Quantum Systems -- 3 Wilson's Renormalization Scheme -- 3.1 Introduction -- 3.2 Kadanoff's Invariance -- 3.3 Wilson's Theory -- 4 Field Theoretical RG -- 4.1 Introduction -- 4.2 Perturbation Theory -- 4.3 Renormalization -- 4.4 Scaling Laws -- 4.5 ?-Expansion -- 4.6 Expansions at d = 3 -- 4.7 Results of Different Approaches -- 5 Generalized RG Approach -- 5.1 Introduction -- 5.2 Scale Transformations -- 5.3 Scale Equations -- 5.4 RG Equations -- 5.5 Applications of Generalized SE -- 5.6 ?-Expansion -- 5.7 Comparison of Different RG Approaches -- 6 RG Study of Particular Systems -- 6.1 Reduction of the Characteristic Set -- 6.2 The Gaussian Model -- 6.3 The Ø4 Model -- 6.4 The Ø4+Ø6-Model -- 6.5 Free Energy in the Critical Region -- 7 Competing Interactions -- 7.1 Heisenberg Magnets -- 7.2 Bicritical Points in Antiferromagnets -- 7.3 Dipole Interaction -- 7.4 Impure Systems -- 8 Exactly Solvable Models and RG -- 8.1 Fluctuation Effects in Spherical Model -- 8.2 Inversion of Phase Transitions -- 8.3 Model with Reduced Interaction -- 8.4 First-Order Transitions -- 8.5 RG and Reduced Interactions -- 9 Application to Copper Oxides -- 9.1 Introduction -- 9.2 La2CuO4 Systems -- 9.3 Oxygen Ordering in ABa2Cu3O6+x -- 9.4 d-Pairing in the Superconducting State -- A Evaluation of Integrals -- A.1 Gaussian Integral -- A.2 A Typical Diagram -- B Local RG -- B.1 General Consideration -- B.2 Spectral Theorems.