XCMS was originally developed to process liquid-chromatography/mass spectrometry (LC-MS) data in metabolomic studies with the R statistics and graphics language (http://www.r-project.org).^1–3 

The main focus of XCMS is the processing of raw data and statistical analysis, but it also has built connections to the METLIN database of the Scripps Institute (http://metlin.scripps.edu), which provides reference spectra for numerous metabolites.^4,5  In addition, XCMS2 enables mass fragmentation (MS/MS) data to be matched against the METLIN reference library.⁶ 

The first releases of XCMS focused on comparing two sample groups, such as a diseased versus a control group. Subsequently, metaXCMS allowed multiple untargeted metabolics datasets to be compared.^7,8