False-colour transmission electron micrograph (TEM) of the Hepatitis B viruses, sometimes called serum hepatitis. Here, the large spheres (known as Dane particles) are the complete virus, with coat and core of the virus visible. Typically Hepatitis B virus occurs in clusters of 3 types of particles (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 the virus, and provide raw material for Hepatitis B vaccines. Hepatitis B infection, sexually transmitted, causes chronic hepatitis. Magnification: x14,250 at 6x7cm size.