The field of lifespan development is ever-changing, and new discoveries are made all the time. As a result, the way we think about and approach development must also change. The new essentials of lifespan development practice are based on the latest scientific research and understanding of how people develop and change over time. Essentials of Life-Span Development These new essentials include a focus on the importance of relationships, experiences and environments in shaping development. Development is not just about individual biology or psychology, but the interaction between all three of these factors. We must also think about development across the lifespan, from infancy to old age. The new essentials of lifespan development practice are essential for anyone working with or studying people.