Incubator temperature is one of the most precious variables in IVF labs. When the IVF started, almost all incubator temperatures were set at 37 degrees which mimic in vivo conditions. Some authors speculated that gametes and early embryos might need low temperatures that provide quieter metabolism. We decide to compare Embryo culture at 37 degree or slightly lower 36.5 degree and extensively investigate to find which is better to crucially introduce a solid evidence through this RCT.