Sami Repo is a professor in Smart Grids area at Tampere University. He has been working with variety of electricity system topics in transmission, distribution and electricity markets almost for three decades. Recently the focus of the research and education has been in the electrification and sector-coupling of the whole energy system and especially in the system of systems analysis of flexibility services needed to maintain the balance of electricity system and to provide hosting capacity for renewable energy and different electrification sectors. Hydrogen has an important role in the indirect electrification of the energy system as an energy carrier and storage in the energy transition to 100 % renewable based energy system.