S100B is a member of the S100 family of calcium-binding proteins, expressed in various glial, neuronal, and peripheral cells. It plays a critical role in brain development by regulating the differentiation, growth, and maturation of glial and neuronal cells. This review summarizes the actions of S100B in the developing brain, focusing on its effects on astrocytes, oligodendrocytes, and neurons. S100B is involved in various biological processes, including cell proliferation, survival, and differentiation, and interacts with the cytoskeleton. It is also involved in calcium signaling and can act as a calcium sensor protein. S100B is found in various brain regions, including the hippocampus, entorhinal cortex, and cerebral cortex, and its expression varies across different developmental stages. S100B is also involved in synaptic plasticity and hippocampus-dependent memory. In addition, S100B has been shown to influence neurodevelopmental processes, including neurite outgrowth, neuronal migration, and the formation of synaptic connections. S100B is also involved in the regulation of astrocyte proliferation and maturation, as well as the development of oligodendrocytes. S100B has been associated with various neurodevelopmental disorders, including Down's Syndrome, and its expression can be affected by factors such as prenatal exposure to stress, ethanol, cocaine, and other environmental factors. The review also discusses the role of S100B in the development of the serotoninergic system and its effects on the development of Purkinje cells and granule cells in the cerebellum. Overall, S100B plays a crucial role in the development and function of the nervous system, and its expression and actions are essential for normal brain development.S100B is a member of the S100 family of calcium-binding proteins, expressed in various glial, neuronal, and peripheral cells. It plays a critical role in brain development by regulating the differentiation, growth, and maturation of glial and neuronal cells. This review summarizes the actions of S100B in the developing brain, focusing on its effects on astrocytes, oligodendrocytes, and neurons. S100B is involved in various biological processes, including cell proliferation, survival, and differentiation, and interacts with the cytoskeleton. It is also involved in calcium signaling and can act as a calcium sensor protein. S100B is found in various brain regions, including the hippocampus, entorhinal cortex, and cerebral cortex, and its expression varies across different developmental stages. S100B is also involved in synaptic plasticity and hippocampus-dependent memory. In addition, S100B has been shown to influence neurodevelopmental processes, including neurite outgrowth, neuronal migration, and the formation of synaptic connections. S100B is also involved in the regulation of astrocyte proliferation and maturation, as well as the development of oligodendrocytes. S100B has been associated with various neurodevelopmental disorders, including Down's Syndrome, and its expression can be affected by factors such as prenatal exposure to stress, ethanol, cocaine, and other environmental factors. The review also discusses the role of S100B in the development of the serotoninergic system and its effects on the development of Purkinje cells and granule cells in the cerebellum. Overall, S100B plays a crucial role in the development and function of the nervous system, and its expression and actions are essential for normal brain development.