MicroRNAs (miRNAs) are small non-coding RNAs that regulate the expression of numerous target genes. Yet, while hundreds of miRNAs have been identified, little is known about their functions. In a recent report published in Silence, Zheng and colleagues demonstrate a technique for robust and specific knockdown of miRNA expression in Caenorhabditis elegans using modified antisense oligonucleotides, which could be utilized as a powerful tool for the study of regulation and function of miRNAs in vivo.