Vitrification is a good way to freeze embryos, but we don't know much about refreezing them. This study looked at refreezing mouse embryos at different stages of development using the CryoLoop method. They found that refreezing embryos did not affect their growth or ability to implant. However, embryos that were not frozen had better hatching rates. The number of cells in the embryos and their ability to develop into different parts were the same in both groups. Overall, refreezing embryos had minimal impact on their development and chances of implantation.