The mesosystem is a concept from ecological systems theory, developed by psychologist Urie Bronfenbrenner. It refers to the interactions and relationships between different microsystems in a person's life, such as family, school, and peer groups. These connections can influence an individual's development and well-being. For example, a child's experience at school can be affected by their home environment. If parents are involved in their child's education, it can lead to better academic performance. Thus, the mesosystem highlights the importance of understanding how various settings, like family and school, work together to shape a person's experiences.