The morphology and crystal structure of Au nanoparticles obtained by irradiating an aqueous solution of Hydrochloroauric acid (HAuCl4) with laser pulses were investigated using transmission electron microscopy, electron diffraction, and electron tomography methods. Along with round and shapeless particles characterized by a cubic structure with twins, there are flat particles with trigonal morphology. Such particles have a layered microstructure, with an alternation of face-centered cubic and close-packed hexagonal crystal structure of layers parallel to the base planes of the prism.