Adenoviruses. Coloured transmission electron micrograph (TEM) of a section through several adenoviruses, a cause of common cold-like infections. They have DNA (deoxyribonucleic acid) genetic material held in a core (magenta), which is surrounded by a protein coat (capsid, blue). Adenovirus infections are common, particularly in children. The adenovirus may also be linked with the transformation of ordinary cells into cancerous ones. Viruses replicate by invading cells and inserting their DNA into the cell's genetic material so that it produces more viruses. Magnification: x15,000 at 35mm size.