Lifespan development refers to the study of how individuals change and grow across their entire lifespan, from infancy to old age. This research area examines the physical, cognitive, emotional, and social changes that occur throughout different stages of life, and how these changes are influenced by genetics, environment, and experiences. Researchers in this field seek to understand how individuals develop and mature, as well as how they respond to challenges and transitions at different points in their lives. Lifespan development research can provide valuable insights into human behavior, relationships, and overall well-being across the lifespan.