The human race has always wanted to look beyond the horizon, to see what is out there.... On either side of us, the Universe has structure on scales up to about a thousand billion billion billion times bigger or smaller than our own. Because this range is not quite infinite, there is hope that we may one day completely understand the structures of the Universe, from the very smallest to the largest we can know. This book describes the remarkable progress we have already made towards this complete picture.... The only thing that seems to be unbounded is the power of reason.