This proposal aims to study the well-defined cobalt-based FT catalysts, with particular attention to the cobalt particle sintering, their crystallographic structure, chemical coordination environment, and the impact of supporting material at the conditions relevant to industrial FT synthesis, including elevated temperatures, pressures, and specific gas compositions, using synchrotron X-ray techniques: wide-angle X-ray scattering (WAXS) and pair distribution function (PDF), used for operando studies of cobalt nanoparticles during FTS.