Metabolomics generates a profile of small molecules that are derived from cellular metabolism and can directly reflect the outcome of complex networks of biochemical reactions, thus providing insights into multiple aspects of cellular physiology. Technological advances have enabled rapid and increasingly expansive data acquisition with samples as small as single cells; however, substantial challenges in the field remain. In this primer we provide an overview of metabolomics, especially mass spectrometry (MS)-based metabolomics, which uses liquid chromatography (LC) for separation, and discuss its utilities and limitations. We identify and discuss several areas at the frontier of metabolomics. Our goal is to give the reader a sense of what might be accomplished when conducting a metabolomics experiment, now and in the near future. Extraction from a biological sample followed by chromatographic separation and mass spectrometry allows the simultaneous measurement of hundreds of metabolites. The application of metabolomics to address numerous biological questions has been successfully demonstrated. Advances in instrumentation and computational tools enable metabolomics. Emerging technologies are further advancing metabolomics.