We are investigating the electronic transport properties of materials, which is a key factor for many applications. We focus on an atomistic description and employ first-principles techniques and to get precise and unbiased results. The increasing power of nowadays' supercomputers and the continuous effort in developing highly efficient codes have made it possible to study systems at realistic industry-relevant sizes, providing valuable insights into the characteristics of these materials. BSC contributes with HPC-related code development as well as assistance with research on tools of various levels of theory. The main contribution to this is the development of TranSIESTA, a first-principles electronic transport simulation tool based on Non-Equilibrium Green's Functions (NEGF). This work is carried out in close collaboration with the SIESTA code developers at the Catalan Institute of Nanoscience and Nanotechnology (ICN2).