Foreword to the special issue on AFM in biology & bionanomedicine.

It is now more than twenty-five years since the initial description of scanning probe microscopy and almost twenty years since the first commercial microscopes found their way into research labs. Currently, we are at a very interesting juncture, during which atomic force microscopy (AFM) is moving from basic research to successful applications in analytical biology and diagnostic medicine. Thus, the timing of this special issue on "Atomic Force Microscopy in Biology & Bionanomedicine", documenting this transition in AFM usage, could not be more appropriate; particularly given the increasing importance of AFM as new or improved methods, reagents, and instrumentation are developed to address outstanding biological questions.