Jerker Widengren (M.Sc. Eng. Physics, M.D., Ph.D.) received his Ph.D. on “Fluorescence Correlation Spectroscopy – photophysical aspects and applications” at the Karolinska Institute, Stockholm, in 1996. In between periods of clinical work as a physician, he did postdoctoral work at the Max-Planck-Institute for Biophysical Chemistry, Göttingen, in single molecule fluorescence spectroscopy with the group of Professor Claus M. Seidel. Since 2003, he has been a professor and the chair of Experimental Biomolecular Physics at the Royal Institute of Technology (KTH), Stockholm. His main research interests are ultrasensitive and ultrahigh resolution fluorescence spectroscopy and imaging for fundamental biomolecular studies and clinical diagnostics.