"Numerous families of non-coding RNAs have been identified in mammalian cells, including lncRNA, miRNA, siRNA, and piRNA. Another type of RNA called circular RNA (circRNA) has remained a mysterious class, as the exact function of these molecules has not been described. Usually, circRNAs result from spicing events and have been identified in plants, animals, and archaea. Recently, Memczak et al. published a paper in Nature reporting evidence that circRNAs tend to show specific expression profiles that are associated with different tissues and developmental phases and function as post-transcriptional regulators."