And yet we've come all that way since then - from single-celled creatures right up to Homo sapiens.

He said, "In sector 39J we encountered a single-celled creature that was many thousands of kilometers across.

These single-celled creatures, long viewed as independent and self sufficient, nonetheless are endowed to lead a rich social life.

If single-celled creatures couldn't survive, it would have to be something very primitive.

Irritation is apparently the only universal sense shared by even single-celled creatures.

The carpet was not a colony of single-celled creatures.

Within those steaming pools, scientists conjecture, may reside the single-celled creatures with which life on earth began some three and a half billion years ago.

We, the People of the Dream, have raised ourselves from single-celled creatures, and from things still lower than the single cells.

The big shift from single-celled creatures to multi-celled ones also happened 800 million years ago.

"If it weren't for evolution I'd be a single-celled creature in the bottom of some swamp."