The congruences of a lattice form the congruence lattice.  Over the last several decades, the study of congruence lattices has established itself as a large and important field with a great number of interesting and deep results, as well as many open problems.  Written by one of the leading experts in lattice theory, this text provides a self-contained introduction to congruences of finite lattices and presents the major results of the last 90 years.  It features the author’s signature “Proof-by-Picture” method, which is used to convey the ideas behind formal proofs...