This study provides a quantitative analysis of the major cell populations in the retina of the C57 mouse. Rod and cone photoreceptors were counted using differential interference contrast microscopy, while horizontal, bipolar, amacrine, and Müller cells were identified using serial section electron micrographs. Ganglion cells and displaced amacrine cells were counted by subtracting the number of axons in the optic nerve from the total neurons in the ganglion cell layer. The results establish a reference for future studies on retinal cell composition. The mouse is a key model for genetic studies, but its central nervous system has been less studied than that of larger mammals. This study aims to clarify the structure of mammalian visual systems, challenging the belief that primate retinas are simpler than those of lower mammals. The results show that retinas of mice, rabbits, and monkeys have similar inner nuclear layer cell populations, contradicting the idea that lower mammals have more complex retinas. The study quantifies the major cell types in the mouse retina: rods (97.2%), cones (2.8%), ganglion cells (41%), bipolar cells (41%), amacrine cells (39%), Müller cells (16%), and horizontal cells (3%). Rods are more abundant than cones, and the distribution of these cells varies across the retina. The study also identifies ChAT-positive amacrine cells, which are distributed in two layers of the retina. The results provide a reference for future studies on retinal cell composition and function. They show that the mouse retina is rod-dominated, with a high density of photoreceptors. The study also highlights the importance of quantitative data in understanding retinal development and function, as well as the impact of genetic manipulations on retinal cell populations. The findings suggest that retinas of lower mammals and primates are not fundamentally different in structure, and that the complexity of retinal processing may be more evenly distributed across species.This study provides a quantitative analysis of the major cell populations in the retina of the C57 mouse. Rod and cone photoreceptors were counted using differential interference contrast microscopy, while horizontal, bipolar, amacrine, and Müller cells were identified using serial section electron micrographs. Ganglion cells and displaced amacrine cells were counted by subtracting the number of axons in the optic nerve from the total neurons in the ganglion cell layer. The results establish a reference for future studies on retinal cell composition. The mouse is a key model for genetic studies, but its central nervous system has been less studied than that of larger mammals. This study aims to clarify the structure of mammalian visual systems, challenging the belief that primate retinas are simpler than those of lower mammals. The results show that retinas of mice, rabbits, and monkeys have similar inner nuclear layer cell populations, contradicting the idea that lower mammals have more complex retinas. The study quantifies the major cell types in the mouse retina: rods (97.2%), cones (2.8%), ganglion cells (41%), bipolar cells (41%), amacrine cells (39%), Müller cells (16%), and horizontal cells (3%). Rods are more abundant than cones, and the distribution of these cells varies across the retina. The study also identifies ChAT-positive amacrine cells, which are distributed in two layers of the retina. The results provide a reference for future studies on retinal cell composition and function. They show that the mouse retina is rod-dominated, with a high density of photoreceptors. The study also highlights the importance of quantitative data in understanding retinal development and function, as well as the impact of genetic manipulations on retinal cell populations. The findings suggest that retinas of lower mammals and primates are not fundamentally different in structure, and that the complexity of retinal processing may be more evenly distributed across species.