In　the　last　decades,　stem　cell-based　regenerative　medicine　has　attracted　intense　attention　and　extraordinary　expectation　due　to　its　potentials　in　the　treatment　of　numerous　major　diseases,　such　as　hepatic,　cardiac,　pulmonary,　renal　and　neurological　diseases.　Clearly　knowing　the　viability,　distribution　and　differentiation　of　the　transplanted　stem　cells　in　vivo　is　a　prerequisite　for　better　understanding　the　role　of　stem　cells　playing　in　the　therapeutic　process,　in　which　the　survival　report　of　the　transplanted　stem　cells　in　vivo　is　particularly　crucial　in　determining　the　success　of　stem　cell-based　regenerative　medicine.　Therefore,　the　development　of　non-invasive　imaging　methods　that　can　in　situ　monitor　the　viability　of　the　transplanted　stem　cells　is　urgently　needed.　In　this　review,　we　summarize　the　recent　progress　in　tracking　the　viability　of　the　transplanted　stem　cells　in　vivo,　including　reporter-gene　based　methods,　exogenous　contrast　label-based　methods　and　multimodel　imaging　methods.　The　reporter-gene　based　methods　rely　on　functional　proteins　that　produce　only　in　live　cells,　thus　the　imaging　signals　are　specifically　coresponding　to　the　viability　of　cells.　Reporter　gene-based　imagings,　including　the　luciferase-based　bioluminescence　imaging　(BLI),　ferritin-based　magnetic　resonance　imaging　(MRI)　and　thymidine　kinase-based　positron　emission　computed　tomography　(PET)　have　been　the　most　robust　technique　for　short-　and　long-term　monitoring　cell　viability　in　vivo.　Herein,　we　explain　basic　principles　of　these　reporter　gene-based　methods,　and　describe　current　examples　and　future　prospects　of　these　methods.　In　contrast　to　reporter-gene　based　methods,　methods　using　exogenous　contrast　labels　such　as　quantum　dots　and　superparamgnetic　iron　oxides　give　a　strong　signal　in　cell　tracking,　but　they　cannot　assess　cell　survival　or　death　for　the　agents　continue　to　display　signals　when　the　transplanted　stem　cells　are　dying.　More　recently,　new　nanotechnologies　using　exogenous　contrast　labels　were　developed　to　monitor　cell　viability　in　vivo,　such　as　the　pH-nanosensor-based　MRI　method,　the　dual-contrast　MRI　method　and　the　fluorescence　imaging　method　using　self-illuminating　nano-probes.　In　this　review,　the　imaging　principles　underlying　these　techniques　are　explained,　and　the　recent　examples　of　exogenous　contrast　label-based　methods　are　described.　Multimodel　imaging　that　combines　the　reportergene-based　technique　and　exogenous　labeling　method,　such　as　the　combined　MRI/PET　method,　PET/BLI　method,　MRI/BLI　method,　or　fluorescence　imaging/BLI　method,　has　been　proposed　to　in　vivo　monitor　both　cell　death　and　cell　viability.　This　review　summarizes　the　recent　development　of　multimodel　imaging　methods,　emphasizes　the　promise　of　the　combined　NIR-II　fluorescence　imaging/BLI　method　and　MRI/PET　method　for　in　vivo　tracking　cell　viability,　and　discusses　the　current　challenges　of　multimodel　imaging.　In　conclusion,　this　review　provides　an　overview　of　the　current　imaging　methodologies　for　cell　viability　tracking,　and　discusses　the　current　challenges　and　further　prospects　of　cell　viability　imaging　methods.　©　2016,　Science　Press.　All　right　reserved.