For thousands of years humans have flirted with understanding space. But now it seems there are so many loose ends in 20th century physics that we are forced to have a closer look at this thing we call space. What we do know from where we stand today, is that virtually everything we thought we knew about space because of our 'common sense' actually turns out to be mostly wrong when you look at the details. This book is a guide to how this search is moving forward, from our common sense ideas to the frontiers of quantum gravity and black hole research.