During the playback of this short time-lapse sequence of CV-1 kidney cells, the tendency of cultured epithelial cells to fasten together into small groups can be observed. This organization is reflective of the behavior of epithelial cells in vivo, where they form tight junctions with one another to produce contiguous epithelial sheets. Over time, the small groups of cells develop into similar sheets in culture.

In actively migrating cells, broad, flattened lamellipodia are typically most prominent along the leading edge. These relatively stationary CV-1 epithelial cells, however, are skirted in lamellipodia almost evenly around their entire periphery. Each cell also features a large round nucleus and easily discernible nucleoli. The granular material encircling the nucleus is comprised of mitochondria. The appearance of the organelles when observed with a light microscope clearly influenced the scientist who coined their name, which stems from the Greek words mitos and khondrion, respectively meaning “thread” and “granule.”

At any given instant, cells appear like static entities under the microscope. It is only through time-lapse studies that the complexity of cell dynamics has begun to be understood. Even mitochondria, which are usually depicted in textbooks simply as inert oblong organelles, are revealed to be extremely flexible and motile in the cells they inhabit during the high speed playback of time-lapse sequences. The mitochondria in the CV-1 cells featured in this video appear to move about the cytoplasm on an almost continual basis.