The spinal dorsal horn plays a crucial role in processing sensory information, particularly pain perception. This region is composed of various neuronal components, including primary afferents, interneurons, and projection neurons, which form complex circuits. Primary afferents, which innervate the skin and deeper tissues, terminate in the dorsal horn with specific patterns determined by their sensory modality. Interneurons, which can be excitatory or inhibitory, process and modulate the signals from primary afferents. Projection neurons, concentrated in laminae I and scattered throughout laminae III-VI, relay information to brain regions involved in pain and temperature perception. The balance between excitation and inhibition is critical for normal sensory function, and disruptions in this balance can lead to conditions like allodynia and hyperalgesia. Recent studies have begun to elucidate the neuronal organization and circuitry of the dorsal horn, providing insights into the mechanisms underlying pain processing and the development of novel analgesics. Despite these advancements, the diversity of neuronal components and the lack of a comprehensive classification scheme remain significant challenges in understanding the dorsal horn's complex circuitry.The spinal dorsal horn plays a crucial role in processing sensory information, particularly pain perception. This region is composed of various neuronal components, including primary afferents, interneurons, and projection neurons, which form complex circuits. Primary afferents, which innervate the skin and deeper tissues, terminate in the dorsal horn with specific patterns determined by their sensory modality. Interneurons, which can be excitatory or inhibitory, process and modulate the signals from primary afferents. Projection neurons, concentrated in laminae I and scattered throughout laminae III-VI, relay information to brain regions involved in pain and temperature perception. The balance between excitation and inhibition is critical for normal sensory function, and disruptions in this balance can lead to conditions like allodynia and hyperalgesia. Recent studies have begun to elucidate the neuronal organization and circuitry of the dorsal horn, providing insights into the mechanisms underlying pain processing and the development of novel analgesics. Despite these advancements, the diversity of neuronal components and the lack of a comprehensive classification scheme remain significant challenges in understanding the dorsal horn's complex circuitry.