The ArgumentThis paper is concerned with the diversity of microscopic research in nineteenth-century life sciences. It examines how two researchers, Ernst Wilhelm Brücke and Heinrich Müller, investigated the structure and function of the retina. They did so in significantly different ways, thereby developing quite different accounts of this organ and its role in the process of vision. Both investigators were carrying out microscopic investigations, both were particularly concerned with interpreting their findings in terms of physiological function, and both employed the (...) physical sciences in their microscopic research. Their approaches differed, however, with respect to the manner of handling and preparing the tissues, as well as with respect to the conceptual tools they applied to their findings.The cases indicate that the common tendency to associate microscopic research mainly with morphological studies of organic material is not appropriate. To understand nineteenth-century microscopy and its place in the sciences of life, close attention should be paid to the manner in which microscopic investigations were performed. It is only then that the flexibility and versatility of microscopic research comes into view. (shrink)