It is possible that physics in the early 21st century is near the possibility of experimental tests of quantum gravity. This is an expository on the subject, where phenomenology and experimental prospects play a crucial part. With the exception of the final three chapters of this book, much of the discussion here may become empirically relevant within a couple of decades. By this it is hoped that the topics will become at best “old physics” in the light of subsequent developments within a few decades into the 21St century. This book is written to become a part of a process that leads to an empirical understanding of quantum gravity, as well as the development of a possible final theory of physics. This final theory may at best be a theory that describes the universe up to the limits of what is understandable. Here there are proposed quantum gravity experiments which could be performed in the next one or two decades. These may help to initiate the study of quantum gravity as a really empirical science.