Many genes in higher eukaryotes can produce circular RNAs (circRNAs) through back-splicing of exons. CircRNAs differ from linear RNAs in their production, structure and turnover and thereby have unique cellular functions and potential biomedical applications. In this talk, I will discuss recent progress in our understanding of the biogenesis, turnover and function of circRNAs. I will also discuss our efforts on developing circular aptamers that can effectively suppress the activation of dsRNA-activated Protein Kinase R (PKR). This has the potential to alleviate inflammation in certain pathophysiological contexts.