2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/16962Our aim in this set of lectures is to give an introduction to critical phenomena that emphasizes the emergence of and the role played by diverging length-scales. It is now accepted that renormalization group gives the basic understanding of these phenomena and so, instead of following the traditional historical trail, we try to develop the subject in a way that emphasizes the length-scale based approach.Revtex, 26 pages, 2 figures. Lectures given at the SERC School on "Field theoretic methods in Condensed matter physics", held at MRI, Allahabad, IndiaStatistical MechanicsHigh Energy Physics - LatticeHigh Energy Physics - Theorytext