miRNAs (microRNAs) were first discovered as critical regulators of developmental timing events in Caenorhabditis elegans. Subsequent studies have shown that miRNAs and cellular factors necessary for miRNA biogenesis are conserved in many organisms, suggesting the importance of miRNAs during developmental processes. Indeed, mutations in the miRNA‐processing pathway induce pleiotropic defects in development, which accompany perturbation of correct expression of target genes. However, control of gene expression in development is not the only function of miRNAs. Recent work has provided new insights into the role of miRNAs in various biological events, including aging and cancer. C. elegans continues to be helpful in facilitating a further understanding of miRNA function in human diseases.