Interfacial electrochemistry of biological molecules and macromolecules such as redox metalloproteins and DNA-based molecules is presently moving towards new levels of structural and functional resolution. Chapters in this volume have illustrated strikingly, first that underlying fundamentals of electron and proton transfer in redox metalloprotein and DNA-based systems are understood but also that new concepts and theoretical challenges are disclosed currently. This applies particularly to interfacial charge transfer in the composite inhomogeneous and anisotropic interfacial solid-electrolyte environment. As also shown, the transition of interfacial pure and applied bioinorganic electrochemistry is emerging out of powerful interdisciplinary efforts. These draw from comprehensive biomolecular electrochemical studies which have mapped working interfacial environments for retaining biological charge transfer function of these highly sensitive macromolecular systems. They have also come to draw from other biotechnology in protein and DNA-molecular functional tuning by use of mutant proteins and DNAbase variability. A complementary line is the introduction of de novo synthetic metalloproteins such as the 4-a-helix heme proteins, electrochemical properties of which have also been studied broadly. The combination of protein and DNA biotechnology with the electrochemical interface has come to offer perspectives towards sophisticated biosensing and bioelectrochemical communication for electrical and other signal transfer between target molecules and external electrochemical circuitry. Strategic surface preparation, functional linker molecules, and biological redox chains of metalloproteins and metalloenzymes are all parts of this. Physical electrochemistry underwent a remarkable evolution from the late 1970's, almost to be likened by a renaissance of electrochemical science.1 This was prompted by close interaction between electrochemistry and both solid state physics and surface science. The introduction of single-crystal, atomically planar electrode surfaces with well-defined surface structures2-5 and sometimes quite simple preparation procedures of such surfaces4,5 were a major breakthrough. This also laid the foundation for other important electrochemical surface techniques and theory. These included spectroscopy (UV/Vis, 6,7 IR,8,9 Raman,10,11 and X-ray photoelectron spectroscopy12), Quartz Crystal Microbalance,13 and other physical techniques, as well as both statistical mechanical14,15 and electronic structural theories and computations,16-18 warranted by the new electrochemistry. Only slightly later the scanning probe techniques, scanning tunneling (STM)19,20 and atomic force microscopy (AFM) 21,22 signalled a lift both of surface science and of interfacial electrochemistry to a new unprecedented level of structural resolution. 23 Atomic resolution of pure metal and semiconductor electrode surfaces, and at least sub-molecular resolution of electrochemical adsorbates could now be achieved, opening new worlds of microscopic structures and processes, and new approaches to electrochemical nanotechnology. Interfacial electrochemistry of proteins and DNA-based molecules is now reaching a level where similar boundary-traversing efforts are visible. As shown by chapters above, recent efforts have pointed to the feasibility of introducing similar state-of-the-art physical electrochemistry into interfacial bioelectrochemistry of redox metalloproteins and DNA-based molecules. At the same time this has increased options for improved voltammetric sensitivity at well-defined electrode surfaces, and for structural mapping of the bioelectrochemical solid-liquid interface to the level of single-molecule resolution. It is remarkable that molecules as large and fragile as redox metalloproteins and metalloenzymes adsorbed on atomically planar electrode surfaces can be mapped to single-molecule resolution in their functional state by a subtle physical phenomenon, the quantum mechanical tunnel effect. These latter observations have opened new approaches to bioelectrochemistry at the levels of well-defined monolayers towards nanoscale and single-molecule levels. These openings have also offered challenges for fundamental theory of electron tunneling through biological macromolecules, the role of the metal centres etc. Environments such as STM directly in aqueous media, essential for control of biomolecular function, and configurations such as limited-size molecular assemblies (ultimately a single molecule) warrant such efforts. These relate both to the finite-size nature of the systems (stochastic as opposed to statistical properties dominating), and to the single-or supramolecular charge transfer patterns in nanogap electrode systems and other novel environments.