This is a mouse fibroblast, showing the actin cytoskeleton in cyan and the interphase nucleus in red. I cultured this cell and prepared the image as described here, using rhodamine-phalloidin and DAPI to stain for filamentous actin and DNA, respectively. Actin helps the cell maintain its shape, and is also plays a critical role in the movement of eukaryotic cells. Here you can see the stable network of actin filaments called stress fibers that diffuse throughout the entire cell, just inside the plasma membrane. Stress fibers end in focal adhesions, allowing the cell to stick to the underlying surface. This solitary cell is attached to the glass microscope slide below, but in tissue it would adhere to the extracellular matrix.