Construction and
commissioning of the cubic-kilometer IceCube neutrino
detector and its low energy extension DeepCore have been
completed. The instrument detects neutrinos over a wide
energy range: from 10 GeV atmospheric neutrinos to 10
10
GeV cosmogenic neutrinos. We will describe
initial results based on a subsample of the more than
300,000 neutrino events recorded during construction. We
will emphasize the measurement of the high-energy
atmospheric neutrino spectrum and the search for the
still enigmatic sources of the Galactic and
extragalactic cosmic rays. Most importantly, we will
discuss how the first data taken with the completed
detector have revealed a flux of extraterrestrial
neutrinos.