Bovine Embryo transfer has been used widely to reproduce the most valuable females in the herd, with about 750,000 embryos produced annually from superovulated donors and more than 450,000 embryos produced using in vitro techniques. Furthermore, embryos are the safest and most cost effective alternatives to move genetics internationally because of their low risk of transmitting diseases. One of most important factors associated with the success and widespread application of this technology is evaluation of the embryos before freezing and/or transfer to a recipient. Embryos are usually classified based on a number code system for their stage of development (1 to 9) and for their quality (1 to 4). The basic principles of embryo evaluation are briefly described