Rod cells are specialized photoreceptor cells located in the retina of the eye. They are responsible for vision in low-light conditions and are highly sensitive to light. Unlike cone cells, which detect color, rod cells provide black-and-white vision and are crucial for night vision. Each rod cell contains a pigment called rhodopsin, which helps convert light into electrical signals that the brain interprets as images. There are approximately 120 million rod cells in the human eye, making them essential for peripheral vision and detecting motion in dim environments.