Immunofluorescent Light Micrograph of squamous carcinoma cells in a colony, cultured from a tumour. Squamous carcinoma is a highly malignant cancer that arises in epithelium: skin, or cells lining the organs of the body. It rapidly invades healthy tissue. Small cells (above centre) are dividing; the large cell below is senescent. Cell nuclei are blue; cytoplasm stains orange; green actin stress fibres form a support network around cells. Immunofluorescence is a staining technique which uses antibodies to attach fluorescent dyes to specific tissues and molecules within the cell. Magnification x400 at 35mm, x750 at 6x4.5cm.