Ganglia are nodular structures in the peripheral nervous system (PNS) that are formed by a cluster of neuron somas. They have important roles in communicating signals from peripheral organs to the nervous system and work as a unique structure of the PNS. As great advances in neuronal manipulation and recording techniques have been made, an increasing amount of research is focused on the function of ganglia. However, ganglion surgery is still very challenging, particularly in small animals such as mice. In the present study, we performed anatomical analyses of two types of sensory ganglia, the dorsal root ganglia and the trigeminal ganglia. Hematoxylin and eosin (H&E) staining revealed structural differences between ganglia and nerve fibers. Immunofluorescence staining with antibodies to neuronal nuclear antigen (NeuN), a neuron-specific marker, labels neurons in ganglia and distinguishes ganglia from other tissues, such as lymph nodes. This study describes the anatomical analysis of the dorsal root ganglia and the trigeminal ganglia, which provides an anatomical basis for functional studies.