Experimentally observed self-organization of a 2D lattice on the surface of Ge single crystal after irradiation by pulsed YAG:Nd laser is reported. The 2D lattice consists of nano-size elevations arranged in a pattern of C-6i point group symmetry and is characterized by translational symmetry with the period of 1 p,m. Calculations of time depended distribution of temperature in the bulk of the Ge sample are presented to explain the phenomenon. The calculations show that overheating of the crystal lattice occurs at laser radiation intensities exceeding 30 MW/cm(2). According to synergetic ideas, the presence of the non-equilibrium liquid phase of Ge and huge gradient of temperature (similar to 3 x 10(8) K/m) can lead to self-organization of the 2D lattice similar to Bernar's cells. (c) 2004 Elsevier B.V. All rights reserved.