MicroRNAs (miRNAs) are a newly identified class of small regulatory non-coding endogenous RNAs that take part in a series of important processes by regulating gene expression. Recent studies have provided evidence that miRNAs may be involved in nearly all biological and metabolic processes, especially influencing self-renewal and differentiation of embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs). In this review, we briefly summarize the biological characteristics of miRNAs, the detection technologies, and the role of miRNAs regulation in ESCs and iPSCs to frame a discussion on the future prospects of miRNA research.