DNA is both a fundamental building block of life and a versatile natural polymer. A myriad of DNA-binding proteins carry out their biological function by recognizing specific shapes and structures of DNA, or by actively altering the DNA configuration through force generation. Single-molecule techniques are ideally suited for studying these interactions thanks to their ability to follow dynamic processes in real time, while precisely exerting and measuring force on the system of interest. In particular, by combining single-molecule fluorescence and force microscopy, we are able to directly correlate the mechanical state of the DNA to the behavior of the protein-DNA complex. These studies emphasize that the physical characteristics of DNA are an integral dimension of biological regulation and unlock new avenues for interrogating genome transactions.