Different types of "Omics" technologies can be combined for a systems biology insight into biological samples. Metabolomics, measurement of the metabolite content of such a system, and transcriptomics, measurement of gene expression, are a preferred combination because of several advantages. Both technologies, especially microarray-based transcriptomics, can be used in routine analysis and are capable of high throughput. In this chapter, we briefly review the process of how metabolomics and transcriptomic data are generated, how they can be combined, and which tools exist for combined analysis. Furthermore, tools for visualization are presented and MassTRIX, a metabolite annotation Web server, also capable of transcriptome data analysis from Affymetrix gene chips, is presented.