Fluorescent phalloidin was used to visualize the actin cytoskeleton of human HeLa cells. In response to the Hsp90 inhibitor geldanamycin, HeLa cells generate cytoplasmic actin stress fibers that span the length of the cells. Filopodia, visualized as finger-like projections from the cell membrane, can also be seen. For details, see the article by Amiri and colleagues 933.