What do you mean by that? Your question is very generic and it´s difficult to propose something.
If you wanna try microscopy, I would recommend MitoTracker Orange CMTMRos, HyPerMito or anti-HSP-70. Investigate every one of them. The decision is yours and it will depend on the strategy you want to follow.
If you want to try with non-microscopic techniques, maybe you should try Sea Horse technology. You should investigate that thechnique too!