We are investigating physiological or pathological roles of cells functioning in living tissues by using in vivo imaging methods including PET, MRI, fluorescence/bioluminescence imaging, microendoscope imaging, electron microscope imaging. In particular, we aim to establish new strategies for treating neurological disorders or malignancy by imaging stem/progenitor cells in the central nervous system or cancer/cancer stem cells. Further, we study metabolic dynamics in pathophysiological states including fatigue, and develop new techniques for controlling the living systems.