** AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** CRYOPRESERVATION IS A CRITICAL TECHNOLOGY TO ENABLE ASSISTED REPRODUCTION IN CATTLE TO ADVANCE GENETIC GAINS. THE PROCESS OF CRYOPRESERVATION CAUSES DAMAGE TO THE EMBRYOS AND A MAJOR CAUSE OF THIS DAMAGE IS THE FORMATION OF ICE CRYSTALS IN THE CELLS. WE WILL TAKE ADVANTAGE OF THE TECHNOLOGICAL ADVANCEMENT IN CRYOPRESERVATION SYSTEMS TO STUDY THE EFFECTS OF COOLING SPEED ON THE AMOUNT OF ICE THAT FORMS IN THE CELL. WE ALSO DEVELOPED A TECHNIQUE TO MEASURE ICE CRYSTAL GROWTH IN THE CELL THAT HAPPENS DURING THE WARMING PROCESS OF CRYOPRESERVED EMBRYOS USING SERIAL IMAGES TAKEN USING SYNCHROTRON X-RAYS. THESE TECHNIQUES ALLOW US TO CHANGE OUR KNOWLEDGE ON THE EFFECTS OF COOLING RATES ON ICE FORMATION DURING COOLING, ICE CRYSTAL GROWTH DURING WARMING, AND THE SURVIVAL OF EMBRYOS AFTER THAWING. THE SECOND OBJECTIVE OF THIS STUDY IS TO DETERMINE IF THE IMPROVED COOLING RATE WILL ALLOW A LOWER CONCENTRATION OF CRYOPROTECTANTS TO BE USED AND STILL MINIMIZE ICE CRYSTAL FORMATION IN CELLS. THIS IS IMPORTANT AS THE CONCENTRATION OF CRYOPROTECTANTS NORMALLY USED AND THAT IS NEEDED TO REDUCE ICE CRYSTAL FORMATION IS TOXIC TO EMBRYOS. BALANCING THE PROTECTIVE BENEFITS OF CRYOPROTECTANTS WITH THE TOXIC EFFECTS MAY BE EASIER WITH THE NEW METHOD OF CRYOPRESERVATION THAT HAS FASTER COOLING RATES. TOGETHER, THESE FUNDAMENTAL KNOWLEDGE ARE CRITICAL IN DEVISING THE NEXT-GENERATION CRYOPRESERVATION METHODS THAT CAN ACCELERATE GENETIC GAINS IN CATTLE.