The article reviews the advancements in the understanding of the Suprachiasmatic Nucleus (SCN) over the past 25 years, following its initial discovery as the central circadian clock. Key developments include the identification of neuropeptides such as arginine vasopressin, vasoactive intestinal peptide, and gastrin-releasing peptide as key players in synchronizing cellular circadian rhythms within the SCN. The discovery of multiple oscillators governing behavioral and physiological rhythms has significantly advanced our understanding of the circadian clock. The interaction between neurons and glial cells has been found to play a crucial role in regulating these rhythms. Methodological advances, such as luminescence and fluorescence reporter techniques, have revealed intricate relationships between cellular and network-level mechanisms. The application of cell type-specific genetic manipulations has provided insights into the functional input-output system of the SCN and its correlation with physiological functions. The review concludes by identifying open questions and challenges that lie ahead, including the role of diffusible signals and the detailed mechanisms of network-level oscillations within the SCN.The article reviews the advancements in the understanding of the Suprachiasmatic Nucleus (SCN) over the past 25 years, following its initial discovery as the central circadian clock. Key developments include the identification of neuropeptides such as arginine vasopressin, vasoactive intestinal peptide, and gastrin-releasing peptide as key players in synchronizing cellular circadian rhythms within the SCN. The discovery of multiple oscillators governing behavioral and physiological rhythms has significantly advanced our understanding of the circadian clock. The interaction between neurons and glial cells has been found to play a crucial role in regulating these rhythms. Methodological advances, such as luminescence and fluorescence reporter techniques, have revealed intricate relationships between cellular and network-level mechanisms. The application of cell type-specific genetic manipulations has provided insights into the functional input-output system of the SCN and its correlation with physiological functions. The review concludes by identifying open questions and challenges that lie ahead, including the role of diffusible signals and the detailed mechanisms of network-level oscillations within the SCN.