Since its early discovery as a messenger, RNA has been shown to play a diverse set of regulatory, structural and even catalytic roles. The more recent understanding that the genome is pervasively transcribed stimulated the discovery of a new prevalent class of long non coding RNAs (lncRNAs). While these are lower abundant and relatively less conserved than other class of functional RNAs, lncRNAs are emerging as key players in different cellular processes in development and disease.