Despite major advances in the biology of aging, there are still no interventions that clearly slow or reverse aging in humans. In contrast, modern medicine already depends on replacement to restore lost function, from artificial joints and cardiac devices to organ transplants and stem cell therapies. This session examines how a similar framework could be applied to aging: rather than repairing deteriorated cells and tissues, scientists and companies are exploring ways to replace them with newly generated, biologically young equivalents. The discussion will highlight emerging capabilities in engineered cell sources, scalable tissue fabrication, and programmable biology (instead of "integration") strategies that are redefining what can be rebuilt and replaced. New approaches are beginning to address long-standing challenges such as age-related signaling environments, vascularization, and even circuit compatibility in parts of the brain. Together, these advances point toward a future where rejuvenation is achieved through deliberate biological reconstruction. The session asks: How far can replacement take us, and could rebuilding youthful parts become a central path to extending healthy lifespan?