Microscopy has revealed tremendous diversity of bacterial and eukaryotic forms. Recent molecular analyses show discor-dance in estimates of biodiversity between morphological and molecular analyses. Moreover, phylogenetic analyses of the diversity of microbial forms reveal evidence of convergence at scales as deep as interdomain: morphologies shared between bacteria and eukaryotes. Here, we highlight examples of such discordance, focusing on exemplary lineages such as testate amoebae, ciliates, and cyanobacteria. These have long histories of morphological study, enabling deeper analyses on both the molecular and morphological sides. We discuss examples in two main categories: (i) morphologically identical (or highly similar) individuals that are genetically distinct and (ii) morphologically distinct individuals that are genetically the same. We argue that hypotheses about discordance can be tested using the concept of neutral morphologies, or more broadly neutral phenotypes, as a null hypothesis. Keywords: .mi crobial evolution; molecular data; morphology; neutral evolution "Thus, we have a neutral-morphology theory of evolution, where a variety of morphologies are equally successful in a particular environment. This makes an interesting contrast to the neutral-gene theory of Motoo Kimura. In the former, for one reason or another, natural selection fails to discriminate among phenotype morphologies, each of which has a distinctive genotype; in the latter, selection fails to discriminate among genotypes that all could have the same phenotype."