Transcriptomics is the high-throughput investigation of the transcriptome, i.e. the set of RNA molecules that are transcribed from the genome under different conditions and/or in different organs, tissues or cell types. Transcriptomics may target the whole RNA population, or a specific subset such as the ribosome bound or the small RNAs. Genes, that are differentially expressed in distinct organs, tissues and cell-types of an organism and/or in response to different environmental, physiological conditions, can be identified by the comparison of transcriptomes.