Gregg Semenza is an American scientist known for his groundbreaking research in the field of cellular biology. He was awarded the Nobel Prize in Physiology or Medicine in 2019 for his discoveries related to how cells sense and adapt to oxygen levels. His work has significant implications for understanding various diseases, including cancer and anemia. Semenza's research focuses on a protein called hypoxia-inducible factor (HIF), which plays a crucial role in regulating genes that respond to low oxygen conditions. His findings have opened new avenues for developing treatments for conditions where oxygen supply is compromised, enhancing our understanding of cellular responses to environmental changes.