False-colour transmission electron micrograph (TEM) of Hepatitis B virus (HBV) particles, the cause of serum hepatitis. Here, the large spheres (known as Dane particles) are the complete virus, with coat and core visible in some examples. Typically HBV occurs in clusters of 3 types of particles (as seen here): the virus itself; smaller spheres and rod-shaped forms made from the protein coat of the virus. These smaller non- infectious particles are antigenically identical to HBV and thus provide raw material for vaccines. Hepatitis B is transmitted sexually & via infected blood. Magnification: x22,000 at 6x7cm size.