Introduction: from the Genome to the Transcriptome

The technologies monitoring the transcriptome are under a continuous status of development and implementation, producing high amounts of expression data which require reliable and well structured databases. This chapter provides a general overview and a reliable guide of these technologies, as developed from the early ‘90s until today, and of the most important available expression databases. The first part aims at introducing to the reader the fundamental functional aspects of these technologies, which are under a continuous development in order to obtain a more accurate description of the transcriptome. The second part offers the necessary information to those who are interested in further exploiting expression data in their research.