The Big Bang theory proposes that the universe we know emerged from a uniformly hot and impenetrable mass of protons, electrons and radiation. But until recently, we knew very little of the first stages of the 13 billion year process in which our cosmos took shape. In 1974, a young astrophysicist, fresh from graduate school at Berkeley, set out to fill in this gap in human knowledge. Leading a small team of researchers at Columbia University's Goddard Center for Space Studies, John Mather devised a proposal for a satellite, the Cosmic Background Explorer (COBE), to measure the microwave background radiation in space. From temperature variations in the radiation emanating from different points in the universe, he hoped to trace the paths of the infant galaxies from their starting point. The scheme seemed far-fetched, and more experienced researchers doubted it would find anything significant, but Mather persuaded NASA to undertake the mission, and was hired by NASA's Goddard Space Flight Center to guide the project. For the next 15 years, Mather led a team of over 1,000 scientists and engineers, designing and building the exquisitely calibrated instruments such an experiment required. In 1989, COBE was launched into space. For four years, the satellite collected its data. Analysis of the data took many years more, but by 1992, Mather had found what he was looking for: cool trails etched in the otherwise uniform background, precisely the "blackbody" patterns predicted by the Big Bang theory. Mather's discovery provides the theory's strongest validation to date. With this data, we can draw a map of the universe as it existed roughly 389,000 years after the Big Bang, "a baby picture of the universe." Mather has chronicled this voyage of discovery in a book for the general public, The Very First Light. Mather's discovery has been hailed as "the missing link in cosmology." The Swedish Academy praised Mather for elevating cosmology to a precision science, and honored his achievement with the Nobel Prize. Mather's work continues. Today, he leads a NASA team building the most sophisticated telescope ever devised. Scheduled for space launch in 2013, we can only guess what wonders it may reveal.