The IceCube Neutrino Observatory includes a tightly spaced inner array in the deepest ice, called DeepCore, which gives access to low-energy neutrinos with a sizable surrounding cosmic ray muon veto. Designed to be sensitive to neutrinos at energies well below 1 TeV, DeepCore will be used to study diverse physics involving neutrinos, including Dark Matter, atmospheric neutrinos and their oscillations. The first year of DeepCore physics data-taking has been completed, and the performance of the detector and the first IceCube observation of atmospheric neutrino-induced cascades are presented.