My principal area of research involves the development and application of numerical modeling to interpret the spectra of the most massive and luminous stars. Due to their high luminosities massive stars shed a significant fraction of their mass during their lifetime. As a consequence material that has undergone nuclear processing is exposed at the stellar surface. Through spectroscopic analyses we can learn about the composition of this material, and hence gain insights into nuclear processes, convection, and stellar evolution, and consequently into the evolution of our galaxy. The research utilizes many different scientific fields including numerical modeling, radiative transfer, radiation–hydrodynamics, polarization, and atomic physics.