I will give an overview of dark matter in galaxies, including some of the smallest dwarf galaxies which are dark matter dominated. For some galaxies, it is possible to measure the central densities and core radii of the dark halos, and they follow scaling laws which have their origins in the shape of the perturbation spectrum of fluctuations in the early universe. The halo scaling relations for the dwarfs also show how the dwarfs have lost baryons during their evolution, and how this baryon loss has affected their structure.