  In the last decade it became clear that methods and techniques based on
supersymmetry provide deep insights in quantum chromodynamics and other
supersymmetric and non-supersymmetric gauge theories at strong coupling. In
this review we summarize major advances in the critical
(Bogomol'nyi-Prasad-Sommerfeld-saturated, BPS for short) solitons in
supersymmetric theories and their implications for understanding basic
dynamical regularities of non-supersymmetric theories. After a brief
introduction in the theory of critical solitons (including a historical
introduction) we focus on three topics: (i) non-Abelian strings in N=2 and
confined monopoles; (ii) reducing the level of supersymmetry; and (iii) domain
walls as D brane prototypes.
