The processing of double-stranded（ds） RNA by RNase III family members is an essential step in the maturation and decay of coding and noncoding RNAs, including miRNAs and siRNAs. RNase III family members share a unique fold （RNase III domain） that can dimerize to form a structure that binds dsRNA and cleaves phosphodiesters on each strand, providing the characteristic 2 nt, 3'-overhang product ends. RNase III converts long double-stranded RNA into a heterogeneous mix of short （18–25 bp） interfering RNAs （siRNA）.