Abstract
Single-molecule microscopy has evolved into the ultimate-sensitivity toolkit to study systems from small molecules to living cells, with the prospect of revolutionizing the modern biosciences. Here we survey the current state of the art in single-molecule tools including fluorescence spectroscopy, tethered particle microscopy, optical and magnetic tweezers, and atomic force microscopy. We also provide guidelines for choosing the right approach from the available single-molecule toolkit for applications as diverse as structural biology, enzymology, nanotechnology and systems biology.