This is the first stage, at the beginning of meiosis, when the chromosomes are visible in the nucleus of the cell.
Professor Robert Edwards explained in an interview the importance of seeing diakinesis - in the early research going back some thirty years , it was the first sign that he was beginning to get the timing of egg development right. "Now diakinesis is desperately important, because it only lasts for 1 or 2 hours therefore if you see diakinesis you have really got a critical stage, you have got the exact stage you want, because that is when the germinal vesicle breaks down and the chromosome appeared in diakinesis. So if I could see diakinesis I was there." That was the turning point in the early research which allowed progress towards IVF.