In this talk, I will try to present a simulation of the growth of cosmic structure in the standard Lambda Cold Dark Matter (LCDM) paradigm. A novel multi-level technique provides a total dynamic range of 30 orders of magnitude in mass, at least 15 orders of magnitude more than any previous calculation and enough to resolve the structure of hundreds of individual dark matter halos with individual masses ranging from that of the Earth to that of a rich cluster of galaxies. For the first time, we are able to characterise the internal structure of present-day halos over the full mass range which is populated if the Dark Matter is a weakly interacting particle of mass 100 GeV. Remarkably we find self-similarity over the full mass range, allowing us to derive the first consistent estimate of how the mean density and mass of halos are related across the entire halo population. Our result differs dramatically from almost all previously published relations, which just extrapolate from simulations of relatively high-mass halos. Our results are important for predicting annihilation radiation signals from dark matter, since these should be dominated by contributions from the smallest structures.
