Of course, in practice we may not be able to apply those principles to how an organism works or to how the human brain works yet. Maybe we never will. But, in general, if one begins to understand these principles down here, one can understand much about how organismic embryologic develop occurs, one can understand a lot about a whole variety of disease processes, one can understand how one inherits disease susceptibilities, and one can understand why many organisms look the way they do, i.e. the process of developmental biology.