Plants and animals are described as opposimilar organisms, inasmuch as they exhibit polarly contrasting morphogenetic processes revolving around a common principle.In effect, the basic morphogenetic logics of plants and animals respectively correspond to those of branching upon branching and invagination within invagination.Repeated morphogenesis thus allows describing both organism types through their several fractal systems and the sequential iteration of said systems.In this context, a striking morphofunctional correspondence reveals that these fractal systems perform opposimilar functions in plants and animals, including extremely precise topological distributions of polarly contrasting biochemical effectors.Due to the complexity of these opposimilarities, so far they constitute an unexplained phenomenon clearly going beyond the Darwinian paradigm.In fact, they call for a revision of the concept of homology, since there seems to be "continuity of information" (cf.Van Valen, 1982) between two natural kingdoms that are said to have diverged from unicellular common ancestors.Some fields with potential explanatory power in this respect are considered.