Random walks: diffusion, current and external forces, solving the diffusion equation. Photon diffusion in the Sun and molecular motors. Temperature and equilibrium. Microcanonical ensamble. Dynamics of phase space. Liouville’s theorem. Entropy as irreversibility. Entropy as disorder. Entropy as ignorance: information and memory. Reversible computations and black hole thermodynamics. Free energy. Canonical ensamble. Uncoupled systems and canonical ensamles. Grand canonical ensamble. Quantum statistical mechanics. Mixed states and density matrix. Quantum harmonic oscillator. Bose and Fermi statistics. Non-interacting bosons and fermions. Maxwell-Boltzman quantum statistics. Black body radiation and Bose condensation. Metals and the Fermi gas. The Ising model. Magnetism, binary alloys, liquids, gases and critical point. Markov chains. Order parameters, broken symetry and toplology. Correlation, response and dissipation. Microwave background radiation. Molecular dynamycs. Damped oscillator. Spin. Abrupt phase transition. Stable and metastable phases. Continuous phase transitions.