False-colour scanning electron micrograph (SEM) of normal human striated muscle fibres. Striated muscle cells are elongated, hence their description as fibres. Each cell has several nuclei (not visible) positioned just below the sarcolemma, the name given to the cell membrane of muscle cells. Running the length of each fibre are contractile proteins arranged in thin threads called myofibrils. More prominent is the banding across the fibres, caused by myofibrils being composed of alternating light & dark sections. Magnification: x1,300 at 6x7cm size, x580 at 35mm size.