A microcrack in a silicon single crystal was experimentally investigated using highresolution transmission electron microscopy (HRTEM). In particular, the numerical Moiré (NM) method was used to visualize the deformations and defects. The lattice structure of the microcrack was carefully observed at the nanoscale. HRTEM images of the microcrack demonstrated that the lattice structure of most of the microcrack regions is regular with good periodicity. In addition, the microcrack cleavage expands alternately along different crystal planes, where the principal cleavage plane is the (1 1 1) crystal plane. The NM maps showed no sharp plastic deformation around the microcrack, but discrete edge dislocations can be found only near the crack tip.