Since the 1970s, a multitude of studies has proven that brain asymmetries are not unique to humans, but a common feature in vertebrate and even in invertebrate species. While the majority of these studies has focused mainly on the behavioral aspect of these asymmetries, an increasing number of studies have also investigated the underlying brain structure of lateralized behavior. In this chapter, we will concentrate on summarizing studies that have applied histological methods to unravel the cellular basis of neuronal lateralization. Two methods have been of particular importance to the field. The first method, neuronal tract tracing, can be used to analyze potential asymmetries in the connectivity pattern of a given area. The second method, immunohistochemistry, has been developed to localize specific neurochemically defined components within tissue slices and has been used to identify asymmetries in number, position, or morphology of specific neuron types, or in the distribution of certain receptors. By providing a detailed description of the theoretical background, applications, required materials, as well as a troubleshooting guide for the most common problems for both methods, we would like to encourage scientists working in lateralization research to perform more studies on the anatomical basis of brain asymmetries.