Scientists recently got excited when the lengthened the petri dish lifetime of human embroyosvuntil,at least 14 days from a previous record of 7 days. The shorter time was sufficient of IVF. But too short understand embroyo development. http://www.npr.org/sections/health-shots/2016/05/04/47653955...

Currently there is a moratorium of embryos longer than 14 days. That is when tissues start differentiating and embroyos has become implanted in the womb.