Protoplasmic astrocytes in the CA1 stratum radiatum of the hippocampus occupy distinct anatomical domains. This study used intracellular dye injection and immunohistochemistry to show that these astrocytes have exclusive territories, contradicting previous assumptions that their processes overlap extensively. GFAP, a common astrocyte marker, only labels about 15% of the total astrocyte volume, suggesting that previous studies may have underestimated astrocyte size and distribution. The results indicate that protoplasmic astrocytes do not interdigitate extensively but instead maintain separate regions, with their processes only coming into limited contact. This finding has important implications for understanding how astrocytes interact with neurons, other glial cells, and blood vessels. The study also shows that protoplasmic astrocytes in CA1 have a complex morphology, with processes extending in various directions and forming distinct boundaries. These findings challenge previous models of astrocyte arrangement and suggest that astrocytes may have specialized functions depending on their location and interactions with neighboring cells. The study also highlights the limitations of using GFAP as a sole marker for astrocyte distribution and emphasizes the need for more detailed imaging techniques to understand astrocyte structure and function. The results suggest that astrocytes may have different roles in different regions of the brain, and that their interactions with neurons and other cells are more complex than previously thought. The study provides new insights into the spatial organization of astrocytes in the brain and their potential roles in neural function.Protoplasmic astrocytes in the CA1 stratum radiatum of the hippocampus occupy distinct anatomical domains. This study used intracellular dye injection and immunohistochemistry to show that these astrocytes have exclusive territories, contradicting previous assumptions that their processes overlap extensively. GFAP, a common astrocyte marker, only labels about 15% of the total astrocyte volume, suggesting that previous studies may have underestimated astrocyte size and distribution. The results indicate that protoplasmic astrocytes do not interdigitate extensively but instead maintain separate regions, with their processes only coming into limited contact. This finding has important implications for understanding how astrocytes interact with neurons, other glial cells, and blood vessels. The study also shows that protoplasmic astrocytes in CA1 have a complex morphology, with processes extending in various directions and forming distinct boundaries. These findings challenge previous models of astrocyte arrangement and suggest that astrocytes may have specialized functions depending on their location and interactions with neighboring cells. The study also highlights the limitations of using GFAP as a sole marker for astrocyte distribution and emphasizes the need for more detailed imaging techniques to understand astrocyte structure and function. The results suggest that astrocytes may have different roles in different regions of the brain, and that their interactions with neurons and other cells are more complex than previously thought. The study provides new insights into the spatial organization of astrocytes in the brain and their potential roles in neural function.