The research programme of circRTrain focuses on circular RNAs (circRNAs), a new large class of non-coding RNAs, which only in very recent years has attracted high general interest. CircRNAs are unique because of their circular structure and, as a consequence, their unusually high stability. Only recent breakthoughs in sequencing technology and computational analyses revealed the widespread existence of circRNAs in animal cells, particularly in neural tissues. Moreover, in aging animal brains the expression of certain circRNAs strongly increases, suggesting connections to age-related diseases. The specific expression of circRNAs in human blood and exosomes make circRNAs attractive biomarker candidates. Understanding circRNAs and exploring their clinical relevance will require to integrate various technologies (sequencing, single-molecule, whole-organism imaging, RNA knockdown/delivery, CRISPR/CAS9), disciplines (biochemistry, computational biology, genetics), model systems (worm, fly, mouse, human) and medical applications (biomarkers and new therapeutic targets and strategies).