Because of its high sensitivity for light elements and the scattering contrast manipulation via isotopic substitutions, neutron reflectometry (NR) is an excellent tool for studying the structure of soft-condensed material. These materials include model biophysical systems as well as in situ living tissue at the solid?liquid interface. The penetrability of neutrons makes NR suitable for probing thin films with thicknesses of 5?5000 � at various buried, for example, solid?liquid, interfaces [J. Daillant and A. Gibaud, Lect. Notes Phys. 770, 133 (2009)
G. Fragneto-Cusani, J. Phys.: Condens. Matter 13, 4973 (2001)
J. Penfold, Curr. Opin. Colloid Interface Sci. 7, 139 (2002)]. Over the past two decades, NR has evolved to become a key tool in the characterization of biological and biomimetic thin films. Highlighted In the current report are some of the authors' recent accomplishments in utilizing NR to study highly complex systems, including in-situ experiments. Such studies will result in a much better understanding of complex biological problems, have significant medical impact by suggesting innovative treatment, and advance the development of highly functionalized biomimetic materials.