In theory they go all the way back to the first single-celled organisms.

Indeed, by weight, these single-celled organisms are worth far more than gold.

For three billion years, life on earth consisted of single-celled organisms like bacteria or algae.

Dopamine has not been detected in bacteria or other single-celled organisms.

Amongst single-celled organisms it may be the dominant form of genetic transfer.

In single-celled organisms, waste products are discharged directly through the surface of the cell.

Gravity has had an effect on the development of animal life since the first single-celled organism.

Leukocytes are different from other cells of the body: they work like independent, single-celled organisms.

The creation of collective beings from single-celled organisms has been going on a long time.

But single-celled organisms can survive for longer and travel farther.