Developments in miniaturized microscopes have ena-bled visualization of brain activities and structural dy-namics in animals engaging in self-determined behav-iors. However, it remains a challenge to resolve activity at single dendritic spines in freely behaving animals. Research teams from Peking University and Institute of Basic Medical Sciences, CAMS successfully developed a fast high-resolution, miniaturized two-photon micro-scope (FHIRM-TPM), and recorded images of neuronal activities at the level of spines in mice experiencing vigorous body movements.