Fig. 4
![Fig. 4](http://media.springernature.com/full/springer-static/image/art%3A10.1186%2Fs12917-017-0980-0/MediaObjects/12917_2017_980_Fig4_HTML.gif)
Transmission electron microscopy (TEM) of SPIO labelled ASCs showing black iron inclusions (red arrows
) in the cytoplasm. a Capture of the moment of endocytosis of SPIO into a cell and formation of a membrane vesicle. b Cluster of SPIO particles within the cytoplasm one week after labelling. c Cluster of SPIO particles within the cytoplasm two weeks after SPIO labelling. (d) SPIO cluster within lysosomes (asterisk
) three weeks after labelling