Each observable U2OS cell exhibits a single rounded nucleus, which contains nucleoli and is surrounded by numerous mitochondria. The mitochondria display a granular appearance in the video. The broad, flattened areas around the periphery of each cell are lamellipodia, surface structures rich in actin filaments that are organized in a manner similar to a net. The narrow, finger-like projections extending out from the cells are filopodia. The actin filaments present in filopodia are arranged into loose bundles held together by fimbrin and other bundling proteins.

Migrating animal cells tend to be broadest along their leading margins, where the pronounced activity of lamellipodia helps drive the cells forward. As demonstrated by the U2OS cells, the posterior regions of the cells usually exhibit a tapered form. A thin strand of material, commonly called a retraction fiber, can often be seen trailing behind the rest of the migrating cells. Retraction fibers exhibit contractile properties and are intermittently lifted from the substratum so that they may be contracted back into the main process of the cell.

Before U2OS cells divide, their shape is drastically altered. When in contact with a flat surface, such as that of an imaging chamber, the cells tend to spread out and display an appearance similar to that of a fried egg. Retraction fibers and other cell surface protrusions are usually contracted prior to mitosis, however, and an approximately spherical form is assumed. The symmetry of the temporary cellular form simplifies the duplication of cellular contents and facilitates their even distribution into new daughter cells, each of which should be identical to the other upon separation. The daughter cells that are formed during this time-lapse sequence quickly settle on the substratum, providing them with a flattened appearance similar to that of their parent cell prior to cell division.