This now-famous image was made in 2003 by NASA's WMAP satellite after it had scanned the entire sky with its extremely sensitive microwave telescopes. Believe it or not this image probes further away, and therefore further back in time, than any of the previous optical images. It reaches back to a time only 380,000 years after the Big Bang, when the expanding fireball had cooled to about 3000 degrees. Had you been alive back then, it would be like standing in the center of a 3000 degree oven - the brilliant light from the incandescent walls would kill you instantly. But as the billions of years passed, that radiation became diluted and reddened by cosmic expansion, so that today the oven appears to be only 3 degrees, with walls glowing gently with microwave emission. It is this microwave emission that the WMAP satellite is seeing - the relic radiation from the Big Bang's brilliant fireball, dimmed and cooled by cosmic expansion. Cosmologists call this "The Cosmic Microwave Background."
This image is also remarkable for its apparent texture; the data have been adjusted to reveal the extremely slight variations in microwave brightness from place to place. These variations show the first signs of lumpiness emerging from the smooth young Universe, so they are the seeds of galaxies and galaxy structures yet to grow. But the patches are much more profound even than this. Although the microwave background itself dates from 380,000 years, the patches we see were imprinted during the actual launch of the expansion itself - the "Bang" of the Big Bang. Current theories suggest that this origin of structure was a quantum mechanical process operating on scales much smaller than an atom, and these tiny variations became blown up huge by cosmic expansion to yield, ultimately, not only the patches on the microwave background, but also the patterns of galaxies we find in today's Universe. This is a truly profound idea that points to the wholeness of nature: the quantum in the cosmic.