This chapter offers a comprehensive examination of DNA single nucleotide polymorphisms (SNPs), which are the most common type of genetic variation among individuals. It begins with an overview of SNPs and the molecular triggers that generate these variations, followed by a detailed exploration of the critical relationship between specific SNPs and human diseases, including sickle cell anemia, β-thalassemia, and various cancers. The chapter systematically categorizes and describes the methodologies for SNP analysis, distinguishing between techniques used for discovering unknown SNPs and those for genotyping known variants. Methods for unknown SNP detection discussed include single-strand conformation polymorphism (SSCP), heteroduplex analysis, denaturing gradient gel electrophoresis (DGGE), enzyme mismatch detection, and high-throughput sequencing. For known SNP detection, the chapter delves into a wide array of assays such as allele-specific oligonucleotide (ASO) hybridization, Clamp-PCR, nucleic acid invasion-based assays, CRISPR-based methods, allele-specific PCR, single nucleotide primer extension, ligation-based methods, and enzyme digestion-based approaches. Furthermore, the chapter highlights the pivotal role of SNPs in the emerging field of precision medicine. It concludes by surveying the broad development and practical applications of SNP technology across diverse fields, including disease diagnosis, animal husbandry, and plant breeding, underscoring its profound impact on genetics and its potential for future advancements.