In MS-based metabolomics, the starting point of data processing is a collection of raw data files, each file corresponding to a single biological sample. A LC-MS data file is a set of sequentially recorded histograms, each representing hits of ionized molecules on the detector during a very small time frame. A histogram is made up of a number of m/z and intensity data points. The basic purpose of data processing is to transform raw data files into representation that assists easy access to characteristics of each observed ion.