The dark matter (DM) that appears to be gravitationally dominant on all astronomical scales larger than the cores of galaxies can be classified, on the basis of its characteristic free-streaming damping mass M_D), as hot (M_D) ~ 10¹⁵M_⊙), warm (M_D ~ 10¹¹M_⊙), or cold (M_D < 10⁸M_⊙) (Bond and Szalay, 1983; Primack and Blumenthal, 1983). For the case of cold DM, the shape of the DM fluctuation spectrum is determined by (a) the primordial spectrum (on scales larger than the horizon), which is usually assumed to have a power spectrum of the form |δk|² ∞ kⁿ (inflationary models predict the “Zeldovich spectrum” n = 1); and (b) “stagspansion”, the stagnation of growth of DM fluctuations which enter the horizon while the universe is still radiation-dominated. Stagspansion flattens the fluctuation spectrum for M ≲ 10¹⁵M_⊙. We report here the results of a numerical evaluation of the fluctuation spectrum in which all relevant physical effects have been included (Blumenthal and Primack, in preparation), together with implications for galaxy formation (Blumenthal, Faber, Primack, and Rees, in preparation; hereafter BFPR).