In contrast to other techniques utilized in physiological studies, calcium imaging can visualize target neurons located deep in the brain. Here, we present a proto-col for one-photon calcium imaging of dorsal and ventral CA1 neurons in head -fixed mice. We describe procedures for injecting GCaMP6f virus, implanting a gradient-index (GRIN) lens, and installing a baseplate for Inscopix microscope mounting.For complete details on the use and execution of this protocol, please refer to Yun et al.1