Ultrafast nuclear magnetic resonance (NMR) uses spatial encoding to record an entire two-dimensional data set in just a single scan. The approach can be applied to either Fouriertransform or Laplace-transform NMR. In both cases, acquisition times are significantly shorter than traditional 2D/Laplace NMR experiments, which allows them to be used to monitor rapid chemical transformations. This Perspective outlines the principles of ultrafast NMR and focuses on examples of its use to detect fast molecular conversions in situ with high temporal resolution. We discuss how this valuable tool can be applied in the future to study a much wider variety of novel reactivity.