Fibroblast cell. Confocal light micrograph of a human fibroblast cell crawling over a glass surface. The cell has been fluorescently stained to reveal the filament proteins actin and vimentin within the green cytoplasm. Fibroblasts are found in connective tissue. They are responsible for producing collagen, the main structural protein in the body. A confocal microscope detects light only from the focal point of its objective lens, allowing thin sections of an intact specimen to be imaged. Magnification; x1000 when printed 10cm wide.