The start-up of the newest and most powerful particle accelerator has started. The Large Hadron Collider (LHC) is the most ambitious undertaking ever attempted in Physics. The scale and complexity of this undertaking are so large it required a truly global effort to realize. The LHC will permit exploration of the fundamental nature of matter and forces by creating conditions similar to those just after the Big Bang. I will introduce some of the questions this instrument is aimed at probing and present some of the challenges of the start-up phase for both the accelerator and the detectors.