Book excerpt: Advancement in the field of nanotechnology has revolutionized the field of medicines and pharmaceuticals in the twentieth century. The proper use of nanomaterials in medical applications requires a proper understanding of these compounds. This correct understanding, beyond the physical and chemical properties, must also have the correct logic of use. In other words, the strategic use of nanomaterials with applicable perspective can also help to advance research, but if we go forward with the current research perspective that leads to the expansion of inapplicable researches, the intrinsic importance of using these nanomaterials is eliminated. This book, considering the importance of nanomaterials and their application in medicine, as well as the significant growth of biomaterials in research fields, introduces the variables law (Rabiee's theory) for the implementation of this research and the establishment of a proper strategy. Considering that the degree of number of biomaterial and host variables follow a variety factors, and by increasing the degree of number of biomaterials and host variables, the degree of total variables also increases and as a result, performance and, consequently, biomaterial behavior in the host environment will have less control and predictive capabilities. For an external substance that is supposed to be in the human body, it must be predictable and controllable, In addition, according to the principle that the host in a fixed person does not have the ability to change, therefore, by using the simpler biomaterials (with less variables), the above goal is more accessible. It should be noted that in addition to observing biocompatibility tests for a biomaterial based on existing protocols and standards, the Applicable Compatibility (AC) parameter is also required in accordance with Rabiee's theory. This book is written in accordance with Rabiee's theory and the contents of this book should be evaluated from this perspective.