The article reviews the recent discoveries and implications of copy number variation (CNV) in the human genome. CNVs, which are large-scale DNA copy number changes, have been found to be prevalent in normal individuals, accounting for a significant portion of genetic variation. The review highlights the importance of CNVs in understanding phenotypic variation, including disease resistance and susceptibility. It discusses the methods used to identify CNVs, such as array-based comparative genomic hybridization (array CGH) and fosmid paired-end sequence comparisons, and the challenges in validating and interpreting CNV data. The article also explores the potential mechanisms of CNV formation, including non-allelic homologous recombination (NAHR) and non-homology-based mutational processes. The clinical implications of CNVs are discussed, emphasizing the need for caution in interpreting their effects on phenotypes. Additionally, the article examines the role of CNVs in evolution and their potential contributions to common diseases. Finally, it outlines the future directions for CNV research, including the development of comprehensive CNV maps and the integration of multiple data sources to better understand the genetic diversity and function of CNVs.The article reviews the recent discoveries and implications of copy number variation (CNV) in the human genome. CNVs, which are large-scale DNA copy number changes, have been found to be prevalent in normal individuals, accounting for a significant portion of genetic variation. The review highlights the importance of CNVs in understanding phenotypic variation, including disease resistance and susceptibility. It discusses the methods used to identify CNVs, such as array-based comparative genomic hybridization (array CGH) and fosmid paired-end sequence comparisons, and the challenges in validating and interpreting CNV data. The article also explores the potential mechanisms of CNV formation, including non-allelic homologous recombination (NAHR) and non-homology-based mutational processes. The clinical implications of CNVs are discussed, emphasizing the need for caution in interpreting their effects on phenotypes. Additionally, the article examines the role of CNVs in evolution and their potential contributions to common diseases. Finally, it outlines the future directions for CNV research, including the development of comprehensive CNV maps and the integration of multiple data sources to better understand the genetic diversity and function of CNVs.