The concept of similarity, and its obverse, dissimilarity, is one of the grand archetypal concepts in all of science. It is ubiquitous within mathematics itself, and equally so in the most remote and far-flung interpretations of mathematics as descriptors of physical reality. Accordingly, it is not easy to grasp in any immediate way all of the ramifications of this concept, and the manifold powerful roles it plays in unification and understanding. We do not therefore attempt any such grand synthesis, but rather a selective illustrated glimpse of similarity manifested in terms of scaling, and dissimilarity in terms of bifurcation between similarity classes. A variety of examples are drawn from biology and technology to illustrate the more formal considerations.