It can hardly be emphasized that one of the most important elements of Special Relativity is the Lorentz transformation. This is the reason why we have spent so much space and effort to derive and study the Lorentz transformation in the early chapters of the book. One could naturally ask “After all these different derivations of the Lorentz transformation why are we not yet finished with it?” The reason is the following. Special Relativity is a geometric theory of physics, which can be written and studied covariantly in terms of Lorentz tensors (four-vectors, etc.) without the need to consider a coordinate system until the very end, when one has to compute explicitly the components of the physical quantities of a problem for some observer.