Modified nucleic acids, sometimes referred to as xenonucleic acids (XNAs), are a promising biotechnology development that have several benefits over conventional nucleic acid treatments. XNAs are perfect for therapeutic and diagnostic applications because of their improved biostability, resistance to enzymatic degradation, and increased binding affinity, which are all a result of chemical modifications. The fact that many XNA-based medications are currently undergoing clinical trials and that several have already obtained regulatory approval shows how important these medications are becoming to medicine. The development of in vitro evolution techniques has also made it possible to screen and optimize XNAs quickly, which has sped up the process of finding high-performance candidates. Enzymatic replication advances have facilitated this progress by making it possible to synthesize and amplify XNA sequences efficiently. Specifically, the author examine the most recent advancements in XNA research in this book chapter.