Fig. 1: Schematic diagram of classifications of circRNAs.
From: Circular RNAs in osteoporosis: expression, functions and roles

According to the biogenesis characteristics from genomic regions, circRNAs are often divided into four types, ecircRNA, EIcircRNA, intergenic circRNAs, and ciRNA. ecircRNA exon circRNAs, EIcircRNA exon–intron circRNAs, ciRNA circular intronic RNA.