The primeval fireball that accompanied the Big Bang is still visible today as a faint microwave glow that fills the sky. This Cosmic Microwave Background (CMB) provides a snapshot of the universe at an age of ~ 0.5 Myr, equivalent to imaging a human being a few hours after conception.
The details of the faint structures visible in the nearly isotropic CMB reveal much about the structure and evolution of the universe. The first resolved images of the CMB were obtained by BOOMERANG, a balloon-borne microwave telescope that circumnavigated the Antarctic.
The BOOMERANG images reveal a universe that is composed of 5% baryonic matter, 30 % non-relativistic dark matter of unknown form, and 65% "dark energy" that is currently causing the expansion of the universe to accelerate.