Cell (biology)

A cell. (TV: The Lie of the Land)

Cells were a part of many living organisms' bodies.

The Doctor once explained, that amino acids would fuse to form cells, which would eventually evolve into plants and animals. (TV: City of Death)

A collection of cells were a cell culture. (COMIC: Culture Shock)

ARC, a companion of the Eleventh Doctor, did not have cells in his body. (COMIC: The Infinite Astronaut)

The process of progenation involved taking a sample of diploid cells, splitting them into haploids, recombining them in a different arrangement and growing the result into an offspring. (TV: The Doctor's Daughter)