Interest in the recently discovered phenomenon of mitochondrial transfer between 
mammalian cells has gained momentum since it was first described in cell culture 
systems more than a decade ago. Mitochondria-targeting fluorescent dyes have 
been repurposed and are now widely used in these studies and in acute disease 
models, sometimes without due consideration of their limitations, while vectors 
containing mitochondrially-imported fluorescent proteins have complemented the 
use of mitochondria-targeting dyes. Genetic approaches that use mitochondrial 
DNA polymorphisms have also been used in some in vitro studies and in tumor 
models and are particularly useful where mtDNA is damaged or deleted. These 
approaches can also be used to study the long-term consequences of mitochondrial 
transfer such as in bone marrow and organ transplantation and in tumour biology 
where inherent mitochondrial damage is often a key feature. As research on 
intercellular mitochondrial transfer moves from cell culture into animal models 
and human diseases it will be important to understand the limitations of the 
various techniques in order to apply appropriate methodologies to address 
physiological and pathophysiological conditions.