In ART treatment, usually laboratories score embryos according to a morphological scoring system to predict their developmental potential. The morphological scoring method is used to score the morphology of embryos at different developmental periods, including 16 ~ 20 h post-fertilization prokaryotic stage embryos, day 3 post-transfer (day3, D3) embryos and blastocysts. Prokaryotic nuclei appeared at 16 ~ 20 h after fertilization, and the scoring system of prokaryotic stage embryos included the evaluation of the number, size, and mutual position of the prokaryotic nuclei, as well as the number, size, and distribution of the nucleolus and cytoplasmic condition of the nucleus. The highest scores and developmental potentials were found in those with two prokaryotic nuclei that were juxtaposed and of the same size, with the same number of kernels in both prokaryotic nuclei, and linearly aligned at the junction of the prokaryotic nuclei. Conjugates with unequal or separated prokaryotes, unequal numbers of nucleoli in both prokaryotes, and irregular distribution had lower scores. Conjugates with multiple prokaryotic nuclei were chromosomally abnormal and were not used for transfer. D3 embryo scoring was used as the main selection criterion for embryo transfer at the cleavage stage.The D3 embryo scoring system is based on the number and arrangement of the cleavage spheres and the proportion of fragments in D3 embryos. Embryos with uniformly sized ovoid globules and no fragmentation have the highest scores. In addition, 8-cell embryos have the highest clinical pregnancy rate, and 8-cell embryos are preferred for transfer. In practice, the selection of embryos is usually combined with prokaryotic scoring and D3 embryo morphology scoring to determine the developmental potential of embryos. Blastocyst culture has the role of screening embryos and helps to improve the clinical pregnancy rate. According to the size of blastocyst cavity and whether it is hatched or not, blastocysts can be categorized into grades 1-6, and grades 3-6 are the blastocysts that can be used for transfer. According to the number of cells and whether they are tightly arranged, the inner cell mass and trophoblast layer are graded A to D. Grade A is the highest and grade D is not used for transfer.