is considered one of the fundamental techniques in molecular biology. It is used to determine the exact order of nucleotide bases in DNA—adenine (A), thymine (T), cytosine (C), and guanine (G). These bases form the genetic code that controls the characteristics and biological functions of living organisms. The principle of DNA sequencing is based on accurately reading this order. The technique initially began with a traditional method known as Sanger Sequencing, which provided precise results but required more time. With scientific advancements, newer technologies such as Next Generation Sequencing have emerged, enabling the analysis of large amounts of DNA quickly and efficiently, thus accelerating scientific research. DNA sequencing has wide applications across various fields. In medicine, it is used to detect genetic disorders and mutations, as well as to diagnose certain types of cancer. It also contributes to the development of personalized medicine, where treatments are tailored according to an individual’s genetic makeup. In agriculture, it helps improve crop quality and increase resistance to diseases and environmental conditions. The importance of this technique lies in its ability to reveal genetic information with high accuracy, helping scientists understand gene function and the causes of many diseases. It has also played a significant role in major scientific achievements such as the Human Genome Project, which successfully mapped the human genome. Despite its significant progress, some challenges remain, including the need for advanced tools to analyze the large volumes of data generated. However, ongoing advancements continue to make this technology more accurate and cost-effective. Conclusion: DNA sequencing is one of the most important achievements of modern science, contributing greatly to medical advancements and the understanding of genetics. Its applications are expected to expand further in the future, serving humanity in many fields. Prepared by: Huda Rafid Abdul Khaleq AL_mustaqbal University is the first university in Iraq