Migrating PL 1 Ut cells and other cultured fibroblasts are often roughly shaped like elongated triangles. The leading margins of the traveling cells are generally broad, being comprised of flattened sheets of membrane-enclosed cytoplasm called lamellipodia. The rest of the cells seem to trail along behind their front edges, tapering backwards into a narrow tail. Known as a retraction fiber, the tail periodically releases its grip on the substratum and is contracted back into the main process of the cell. Frequently the contraction of the fiber is rapid, like a piece of elastic that snaps back into place after it was stretched too thin.

Several raccoon uterus fibroblasts can be observed undergoing cell division during the high speed playback of the time-lapse sequence. Before the cells undergo the process, they retract their lamellipodia and other surface extensions, giving them a roughly spherical form. Newly produced daughter cells generally experience blebbing of their surfaces, as their initial spherical geometries adapt and settle on the substratum. The dynamics of the small, hemispherical blebs can create the impression that the surfaces of the cells are boiling.

Nuclei, mitochondria, and other organelles are generally located in the main process of a cell rather than along its margins, where lamellipodia and other surface extensions are formed, as exemplified by the PL 1 Ut fibroblasts. The differences in the cytoplasm located in the different regions of the cell are thought to be partially responsible for this phenomenon. In the central region of a cell, the cytoplasm (termed plasmasol) exhibits many of the characteristics of a fluid and permits the dynamic behavior of organelles. Along the cell periphery, however, cytoplasm characteristically exhibits gel-like properties and is known as plasmagel.