Solution NMR / Structure / Dynamics / InteractionsHigh resolution liquid state nuclear magnetic resonance spectroscopy (NMR) is a powerful technique for in vitro studies of structure and dynamics of soluble biological macromolecules under physiological conditions. The unique combination of atomically resolved structural data with both local and global dynamic features covering the entire range of time scales from picoseconds to seconds makes NMR the method of choice in a very diverse and rapidly growing array of biochemical, biomedical, and pharmaceutical applications. After briefly introducing the basic principles of liquid state NMR we review recent methodological and instrumental advances in the field of biologically focused high resolution NMR. The main emphasis of the second part is on molecular interactions. Such interactions are fundamental for the function of proteins in living systems, e.g. for signal transduction, enzymatic catalysis, and immune defense. The tremendous opportunities of high resolution NMR in the identification and detailed characterization of the sites and modes of molecular interactions will be demonstrated.