We give a short review of some known and new results related to harmonic maps. In particular, we generalize classical Dirichlet's principle, area theorem, theorems of uniqueness of harmonic maps, Bloch theorem, estimates for the modulus of the derivatives of harmonic univalent mappings, etc. We use different tools: Dirichlet's principle, minimizing sequences, different versions of Reich--Strebel inequality, area theorem, etc. Also, a comprehensive outline of proofs for most of new results is given.