E M Lifshitz's theory of fluctuation molecular forces (Zh. Eksp. Teor. Fiz., Vol. 29, p. 94, 1955 [Sov. Phys. JETP, Vol. 2, 73, 1956]) and related problems are introduced from a historical perspective. Applications of the theory to soft matter physics are discussed, together with some new predictions (for example, the stability of smectic or cholesteric liquid crystal films).