Preliminaries. Fundamental Concepts and Postulates of Statistical Mechanics. Liouville Equation and Liouville Theorem. Ensembles and Partition Function. Fluctuations and Response Functions. Ideal Monatomic Gas: Translational Entropy. Ideal Gas of Diatomic Molecules: Rotational and Vibrational Entropy and Specific Heat. Interacting Systems: Lattice Models. Cell Theory of Liquids. Distribution Functions of Liquids. Hard Spheres. Perturbation Theories of Liquids with Continuous Potential. Phase Transitions: Basics. Landau Theory of Phase Transitions. Critical Phenomena and Renormalization group. Microscopic Approach towards Phase Transitions. Theory of Freezing and Melting. Nucleation. Growth and Aggregation. Spinodal Decomposition. Binary Mixtures. Energy Landscapes and Inherent Structures of Liquids and Glasses. Polymer in Solutions and Polymer Collapse. Polymer Folding and Crystallization. Liquid Crystals. Quantum Statistics and Bose-Einstein Condensation. Quantum Theory of Solids. Surfactants. Free Energy Calculations Using Computer Simulations. Appendix-A: Maximum Term Method. Appendix-B: Boltzmann H-theorem.