This article is the last of four articles that summarize a broad theoretical research work. The first three articles intended to investigate the nature and characteristics of the Entity of the Electric Charge. The first two parts of this research, dealing with Electric Charge, Energy, and Space, were already completed, and published in two articles [6], [7]. The first article concluded that the Electric Charge is a form of Energy, similarly to Mass being recognized as a form of Energy by Einstein's Special Relativity Theory. And since all the tangible, concrete and perceptible matter in the universe is composed of only two Entities: Mass and Electric Charge, then, the first article concluded that all the tangible, concrete and perceptible matter in the universe is just a form of Energy. The Second article provided a reasonable explanation to the mysterious Dark Energy and concluded that also Space might be a form of Energy. The third article was also completed, and it studied the origins of the Electrically Charged Bodies' Interactions. It provided an explanation to what causes the Attraction/Repulsion between Electric Charges, similarly to the explanation of Einstein's General Relativity Theory to what causes the Attraction between Mass Objects. As such, the third article is an expansion of Einstein's General Relativity Theory to include in it not only Mass Objects but also Electric Charges. This article, which, as stated above, is the fourth in this theoretical research work, derives additional conclusions from all the previous articles, with the most significant conclusion being that Nature, or the Existence, is composed of only one distinct and independent Entity: Energy. All other Entities used by Physics in order to understand or explain Nature, are actually redundant, and are necessary only to help us precept Nature, and, this article concludes, that all these other Entities are facets of Energy, or tools we use to explain how Energies convert from one form of Energy to another form of Energy, and how forms of Energies interact with each other.