Fibroblast cells. Immunofluorescence micrograph of fibroblast cells. The cell nuclei, which contain the cells' genetic information, are blue. Microtubules, protein filaments that make up part of the cytoskeleton, are green. The cytoskeleton maintains the cells' shape, allows some cellular mobility and is involved in intracellular transport. Cell-cell contacts are red. These allow communication between the cells and regulate cell growth. Fibroblasts are cells that give rise to connective tissue such as collagen, the main structural protein in the body. They are important in wound healing. Magnification: x9000 when printed at 10 centimetres wide.