In the case of spontaneous (upon cooling) γ - α martensitic transformation in iron alloys, the formation of a martensitic crystal is determined by a controlling wave process and proceeds at supersonic speed with respect to longitudinal waves. The initiation of three-dimensional threshold deformation is associated with the coordinated action of relatively long-wavelength ℓ-wave and relatively short-wavelength s-waves. For the description of habitus planes, ℓ-waves that arise during the formation of the initial excited state (IES) are responsible. This approach is effective both in describing twinned crystals and in the limiting case of a degenerate twin structure comparable to the formation of dislocation crystals at grain sizes of the initial γ-phase exceeding critical Dc values. In the case of the nanocrystalline state, variants of the transformation of grains as a whole are observed, provisionally associated to the accommodative martensitic transformation (AMT). The critical Dac size for AMT is less than Dc. In dynamic theory, the value of Dac can be associated with the process of spatial scaling of the IES, which is compared with the propagation of cylindrical and spherical waves for a relative change in volume. In such a transformation scenario, the size of the Dac, as well as the critical size for the transformation of small free particles, is determined by the threshold deformation value.