Retrovirus infection. Coloured transmission electron micrograph (TEM) of a section through a myeloma cancer cell infected with a retrovirus. The cell is coloured green with it's nucleus at upper right. At lower right small red retrovirus particles are seen both within and outside the cell. These have infected and taken over the cell, forcing it to produce more virus particles. Retroviruses are a family of viruses made of a protein coat enclosing RNA-genetic material. They cause diseases such as AIDS (acquired immune deficiency syndrome) and leukaemia. Magnification: x5,500 at 6x7cm size. Magnification: x18,000 at 8x10 size."