Figure 1 - A rat lung cell attempting to ingest carbon nanotubes that are longer than the distance that the cell can stretch, which means that the rat cannot remove such nanotubes from the body.

This optical microscopy image is superimposed with confocal images of the protein cytoskeleton that gives the cell structure and its ability to move. F-actin is shown in red; tubulin in green. (Image provided by D. Brown, Napier Univ. and I. Kinloch, Univ. Manchester).