1.Which types of non-thermal energy dominate in the chromosphere and beyond?

2.How does the chromosphere regulate mass and energy supply to corona and heliosphere?

3.How do magnetic flux and matter rise through the lower atmosphere, and what role does flux emergence play in flares and mass ejections?

The complex processes and enormous contrasts of density, temperature and magnetic field within this interface region require instrument and modeling capabilities that are only now within reach. The IRIS team will use advances in instrumental and computational technology, its extensive experience, and its broad technological heritage to build a state-of-the-art instrument to provide unprecedented access to the plasma-physical processes in the interface region.