The 'Beginner's Guides' are an ongoing series of feature articles, each one covering a key technique and offering the scientifically literate, but not necessarily expert audience, a background briefing on the underlying science of a technique that is (or will be) widely used in molecular bioscience. The series will cover a mixture of techniques, including some that are well established amongst a subset of our readership but not necessarily familiar to those in different specialisms. This 'Beginner's Guide' covers nuclear magnetic resonance. Nuclear magnetic resonance (NMR) provides a way to explore the 3D structures of macromolecules in much more biologically relevant conditions and does this by taking advantage of the quantum mechanical property of some nuclei---nuclear spin. Here, we discuss how nuclear spin can be harnessed to provide information on the 3D structure of macromolecules in solution and how new thinking is leading to a revolution in drug discovery.