As this book is being completed, the Large Hadron Collider (LHC) at CERN, and its two large detectors, ATLAS and CMS, are nearing completion. The center of mass energy at this machine will be large, about 14 TeV. The center of mass energies of the partons – the quarks and gluons – within the colliding protons will be larger than 1 TeV. The luminosity will also be very large. As a result, if almost any of the ideas we have described for understanding the hierarchy problem in Part 1 of this book are correct, evidence should appear within a few years. For example, if the hypothesis of low-energy supersymmetry is correct, we should see events with large amounts of missing energy, and signatures such as multiple leptons. Large extra dimensions should be associated with rapid growth of cross sections for various processes, again with missing energy; the warped spaces suggested by Randall and Sundrum should be associated with the appearance of massive resonances. Technicolor, similarly, should lead to broad resonances. Assuming some underlying technicolor model can satisfy constraints from flavor physics and precision electroweak measurements, one might expect to find some number of light (compared with 1 TeV), pseudo-Goldstone bosons, many with gauge quantum numbers. If any of these phenomena occur, distinguishing among them in the complicated environment of a hadron machine will be challenging. It is conceivable that there will be competing explanations, and that choosing between them will require a very high-energy electron–positron colliding beam machine. Such a machine is under consideration by a consortium of nations, and is referred to as the International Linear Collider, or ILC.