After obtaining his PhD in Biomolecular Mass Spectrometry in the lab of Albert Heck, Eef continued his career in (the pharmaceutical) industry. He consecutively worked for Organon (as a post-doc), Philips Research and MSD (Merck) and is currently Group Leader Extended Characterization at Byondis BV. The main focus of his work is (and has been) obtaining insight into the higher order structure of complex biomolecules, such as antibodies and antibody-drug conjugates, by combining mass spectrometric and spectroscopic techniques. In this way, Eef contributes to the development of efficacious and safe compounds that are destined to address unmet medical needs.