False-colour transmission electron micrograph (TEM) of lambda bacteriophages (phages), a type of virus that only infects bacterial cells. Lacking any reproductive machinery themselves, they infect bacteria & commandeer their cellular apparatus for purposes of replication. The genetic material (DNA) of the phage is contained within the head, an icosahedral figure (some coloured green, others pink). Each head is attached to a (linear) tail, which in this species is noncontractile. Phages of human faecal bacteria may cause malabsorption if released in sufficient quantities. Magnification: x18,000 at 6x7cm size.