The term pre-embryo is useful in the political arena - where decisions are made about whether to allow early embryo (now called pre-embryo) experimentation - as well as in the confines of a doctor's office, where it can be used to allay moral concerns that might be expressed by IVF patients. 'Don't worry,' a doctor might say, 'it's only pre-embryos that we're manipulating or freezing. They won't turn into real human embryos until after we've put them back into your body.'