Atomic force microscopy (AFM) was used to directly investigate the morphology and mechanical properties of blastomeres during the embryo development. With AFM imaging, the surface topography of blastomeres from two-cell, four-cell, and eight-cell stages was visualized, and the AFM images clearly revealed the blastomere's morphological changes during the different embryo developmental stages. The section measurements of the AFM topography images of the blastomeres showed that the axis of the embryos nearly kept constant during the two-cell, four-cell, and eight-cell stages. With AFM indenting, the mechanical properties of living blastomeres from several embryos were measured quantitatively under physiological conditions. The results of mechanical properties measurements indicated that the Young's modulus of the two blastomeres from two-cell embryo was different from each other, and the four blastomeres from the four-cell embryo also had variable Young's modulus. Besides, the blastomeres from two-cell embryos were significantly harder than blastomeres from four-cell embryos. These results can improve our understanding of the embryo development from the view of cell mechanics. © 2013 John Wiley & Sons, Ltd.