Introduction The bending of DNA strands is a common phenomenon either intrinsic or induced by protein binding and/or other changes in the physiological environment (such as local ion concentrations). It is believed to play an important role in the control of gene expression, replication, recombination, and packaging in the nucleus. Kinking, roughly defined as abrupt bending, is a distinct category of DNA bending and is often observed in protein-DNA complexes. Numerous methods are available to detect structural fluctuations in DNA. To clearly distinguish between smoothly distributed bending and highly localized kinking, however, a spatial resolution on the order of at least 1 nm is required. Among many high-resolution imaging tools, the atomic force microscope (AFM), with easy sample preparation and close to native imaging conditions, stands out as one of the best options for biologists. Its near- atomic resolution makes it useful for in situ imaging of conformational changes in DNA molecules. Due to tip-broadening effects, however, the width of DNA molecules obtained with atomic force microscopy has been on the order of 5 nm.