This article introduces a new physical law that I shall call The Scale Law, The Scaling Law, or The Scale Principle. This law, which is a Model Meta-law, is a model all the laws of physics must obey. The paper shows that the Scale Law can produce true descriptions of nature (exact laws) through two examples: (a) the Heisenberg uncertainty principle and (b) the black hole entropy. Further research I carried out showed that all normal laws of physics are special cases of this formulation. The Scale Law may be used (a) to find exact laws of physics. This is only possible if we know all the necessary information about the phenomenon we are trying to describe. I have illustrated this point in another paper where I derived the Lorentz transformations from the Scale Law [18]; and (b) to find numeric laws of physics. This case applies when we do not know all the information about the phenomenon we try to describe and therefore we may only find a numeric equation for the phenomenon. In order to illustrate the Scale Law more thoroughly, I introduced two numeric formulas for the proton radius. The first formula, which is likely to be numeric, suggests that generation 1, which makes up all the normal matter in the universe, exists because of the existence of the other two generations and the structure of the universe at the Planck scale. The second formula, which is likely to be more accurate and perhaps exact, matches the proton radius obtained by Lamb shift measurements in muonic hydrogen. Finally, based on a table of scale factors, the formulation predicts the size of the electron within a small range of possible values. This result is backed up by a separate prediction I made of the size of the electron based on an electron model with an infinite potential well [12]. Thus, the Scale Law opens a new window into the understanding of all levels of Nature.