Eye lens fibres. Coloured scanning electron micrograph (SEM) of a freeze-fracture of a lens of an eye, showing the regular arrangement of fibres. Lens cells lack a nuclei, and the main constituent of the cells is the protein crystallin. Tightly packed layers of lens fibres (as seen here) are referred to as laminae. The transparency of the lens is thought to arise from the regular arrangement of the cells and fibres. Magnification: x700 when printed at 10 centimetres wide.