Coloured scanning electron micrograph (SEM) of a freeze-fracture through muscle tissue. The dark red units are muscle fibres, which have a striped appearance due to the many individual units of contractile filaments called myofibrils. Each fibre is surrounded by endomysium connective tissue (grey), which contains nerve cells and capillary blood vessels (beige). Erythrocytes, or red blood cells, (red) can be seen in some of the capillaries. The picture was created as part of a cooperation with Quintessenz Publishing. Magnification: x2,500 when printed at 15 centimetres wide.