Metabolomics aims to identify and quantify the full range of chemical metabolites present in cells and organisms. As there are many hundreds of metabolites present in every cell, and the levels of these metabolites can vary greatly in response to genetics and the environment, this is a mammoth task. Scientists are investigating the complex world of metabolites using techniques such as gas chromatography and liquid chromatgraphy linked to mass spectrometers. Other scientists use nuclear magnetic resonance to probe the structures of complex metabolites.