One of the best neurohistologic methods to reveal the cytoarchitecture of the brain and detailed morphology of neurons with unsurpassed clarity has been the Golgi staining. It is based on the principle of metallic impregnation of neurons, allowing visualization in their entirety including cell soma, axons, dendrites, and spines. In this chapter, we describe the Golgi-Cox protocol standardized in our laboratory that can be used to study experimental effects of different genetic manipulations on spatial distribution of neurons, dendrite density, spine number and morphology to elucidate gene functions during development and in adult brain.