This article, authored by Craig Moritz and Carla Cicero, discusses the concept of DNA barcoding, particularly its application in identifying and discovering new species. DNA barcoding aims to use a single or a few reference genes, such as the cytochrome *c* oxidase I (COI) gene, to assign unknown individuals to species and aid in the discovery of new species. The authors highlight the potential benefits of DNA barcoding, including the development of a comprehensive database of sequences for species identification. However, they also address the controversies surrounding DNA barcoding, emphasizing that it should be integrated with existing taxonomic practices and that single-gene sequences should not be the sole identifier for species. The article critiques the initial enthusiasm and subsequent criticism of DNA barcoding, noting that while it can enhance precision and efficiency in field studies, it should not be confused with resolving the "tree of life." The authors argue that DNA barcodes have limited phylogenetic resolution and that their use should be within the broader context of systematics, including the importance of voucher specimens and integrating molecular and morphological characters. The authors evaluate the validity of DNA barcoding through a study of North American birds, where COI sequencing was used to test the correspondence between species boundaries signaled by barcodes and those established by prior taxonomic research. They find that while COI sequences can distinguish closely related species, they may not always accurately identify genetically divergent taxa. The article also discusses the limitations of using mtDNA divergence as a primary criterion for species boundaries, highlighting the need for a more nuanced approach that considers multiple lines of biological evidence. Overall, the authors conclude that while DNA barcoding has significant potential, it requires further refinement and broader application to address its limitations and to ensure its utility in both individual identification and species discovery. They emphasize the need for more detailed analyses, particularly in regions with complex phylogeographic structures and in groups with frequent hybridization and high rates of gene transfer.This article, authored by Craig Moritz and Carla Cicero, discusses the concept of DNA barcoding, particularly its application in identifying and discovering new species. DNA barcoding aims to use a single or a few reference genes, such as the cytochrome *c* oxidase I (COI) gene, to assign unknown individuals to species and aid in the discovery of new species. The authors highlight the potential benefits of DNA barcoding, including the development of a comprehensive database of sequences for species identification. However, they also address the controversies surrounding DNA barcoding, emphasizing that it should be integrated with existing taxonomic practices and that single-gene sequences should not be the sole identifier for species. The article critiques the initial enthusiasm and subsequent criticism of DNA barcoding, noting that while it can enhance precision and efficiency in field studies, it should not be confused with resolving the "tree of life." The authors argue that DNA barcodes have limited phylogenetic resolution and that their use should be within the broader context of systematics, including the importance of voucher specimens and integrating molecular and morphological characters. The authors evaluate the validity of DNA barcoding through a study of North American birds, where COI sequencing was used to test the correspondence between species boundaries signaled by barcodes and those established by prior taxonomic research. They find that while COI sequences can distinguish closely related species, they may not always accurately identify genetically divergent taxa. The article also discusses the limitations of using mtDNA divergence as a primary criterion for species boundaries, highlighting the need for a more nuanced approach that considers multiple lines of biological evidence. Overall, the authors conclude that while DNA barcoding has significant potential, it requires further refinement and broader application to address its limitations and to ensure its utility in both individual identification and species discovery. They emphasize the need for more detailed analyses, particularly in regions with complex phylogeographic structures and in groups with frequent hybridization and high rates of gene transfer.