Keratinocytes. Immunofluorescent light micrograph of embryonic keratinocyte skin cells. The nuclei of these cells are blue. Green coloured phosphtyr- osine proteins are seen around the nuclei. These are the precursors of melanin, the pigment which colours the skin. Red stained vinculin is a protein found in dividing cells. These cells are known as primary keratinocytes, found in embryonic tissue, they will eventually produce the protein, keratin which is found in hair, nails and horny tissue. Immunofluorescence is a staining technique which uses antibodies to attach fluorescent dyes to specific cells and molecules. Magnification:x374 at 4.5x6cm size.