Split-inteins are a subset of inteins that are expressed in two separate halves and catalyze splicing in trans upon association of the two domains. They occur naturally and have also been artificially generated by splitting of contiguous ones. With their unique properties, split-inteins offer improved controllability, flexibility and capability to existing tools based on contiguous inteins. In addition, split-inteins have proven useful in several new applications. This review gives a general introduction to split-inteins with a focus on their role in expanding the applications of intein-based technologies.