The work under way was not even with human cells.

I could build something the size of a human cell.

I haven't been able to culture it with any human cells.

And I never saw anything like this in a human cell before.

Human cells in an animal brain could also be a problem.

It then grows human cells in a culture to produce the drug.

Scientists had been trying to keep human cells alive in culture for decades, but they all eventually died.

By their very nature they were designed to pierce the walls of human cells.

But this requires a far deeper understanding of human cells than is yet at hand.

There are a billion protein molecules in an average human cell.