In Bronfenbrenner's model what is the mesosystem?

The mesosystem consists of the INTERACTIONS among the elements of the microsystem, and healthy development depends on how effectively the elements work together (Lee, 2010; Lerner, Lewin-Bizan & Warren, 2011). For example, schools that promote high levels of parental involvement provide a more effective environment for development than those that don't (Lezotte &Snyder, 2011; O'Connor, Dearing & Collins, 2011).