The article provides an overview of microRNAs (miRNAs), which were first discovered over 20 years ago and have since been identified as a critical class of small noncoding regulatory RNAs. MiRNAs play a crucial role in gene expression regulation, with over 2000 identified in humans and estimated to regulate one-third of the genome. The canonical miRNA biogenesis pathway involves the processing of primary miRNA transcripts by the enzymes Drosha and Dicer, followed by loading into the RNA-induced silencing complex (RISC). MiRNAs target mRNAs for translational repression or degradation, often through complementary base pairing with the "seed" region of the mRNA. The article discusses alternative biogenesis pathways, target identification methods, and the regulation of miRNA production. It also highlights the biological roles of miRNAs in various tissues and their dysregulation in diseases such as cancer, metabolic disorders, and viral infections. Additionally, the potential of miRNAs as diagnostic markers and therapeutic targets is explored, including the development of miRNA-based diagnostics and the use of miRNA mimics and inhibitors for therapeutic purposes. Finally, the article touches on genome editing approaches using CRISPR/Cas technology to target miRNA genes.The article provides an overview of microRNAs (miRNAs), which were first discovered over 20 years ago and have since been identified as a critical class of small noncoding regulatory RNAs. MiRNAs play a crucial role in gene expression regulation, with over 2000 identified in humans and estimated to regulate one-third of the genome. The canonical miRNA biogenesis pathway involves the processing of primary miRNA transcripts by the enzymes Drosha and Dicer, followed by loading into the RNA-induced silencing complex (RISC). MiRNAs target mRNAs for translational repression or degradation, often through complementary base pairing with the "seed" region of the mRNA. The article discusses alternative biogenesis pathways, target identification methods, and the regulation of miRNA production. It also highlights the biological roles of miRNAs in various tissues and their dysregulation in diseases such as cancer, metabolic disorders, and viral infections. Additionally, the potential of miRNAs as diagnostic markers and therapeutic targets is explored, including the development of miRNA-based diagnostics and the use of miRNA mimics and inhibitors for therapeutic purposes. Finally, the article touches on genome editing approaches using CRISPR/Cas technology to target miRNA genes.