The NCSR “DEMOKRITOS” is the oldest and largest research facility in Greece. It covers a wide gamut of scientific research from Nuclear Technology to microelectronics, material science and biology. The “Thermal – Hydraulics and Multiphase Flow Laboratory” (THEMLAB) has conducted significant computational work on inhalation dosimetry and lung deposition of micro- and nano-particles (of various physicochemical characteristics), and has successfully introduced sophisticated and innovative methodologies for the computer modelling of blood flow. The group participates in the mirror Technology Platform (at national level) of the European Technology Platform on Industrial Safety (ETPIS), having as particular mandate to coordinate, at national level, the Focus Group on Nanosafety (FG7). The laboratory is equipped with advanced computer infrastructure consisted of cluster and grid computing hardware (cluster THALES, permitting more than 160 parallel processes).