1. The importance of water electrolysis for our future energy system 2. Basics of water electrolysis 3. Comparison with other hydrogen production processes 4. Historical outline of water electrolysis 5. Alkaline water electrolysis (AWE) 6. PEM water electrolysis (PEMWE) 7. High-temperature steam electrolysis (SOSE) 8. Chlor-alkali electrolysis 9. Seawater electrolysis 10. Economics of water electrolysis 11. Regenerative FCs 12. Selected projects for system integration 13. Hydrogen storage