At day 5 or 6 of culture embryos reach the blastocyst stage. At this time a laser-assisted biopsy is performed for pre-implantation genetic diagnosis. In other words, a very small piece of the trophectoderm is taken for analysis using a procedure capable of analyzing the entire chromosomes content (23 pairs). This technique allows patients and physicians to transfer embryos that are known to be genetically normal. The video shows a blastocysts hold into position and a biopsy micro-pipette applying suction while the laser is separating the cells for analysis at 400X magnification.