Hydration of natural hydraulic lime binder where gel-like C-S-H phases are developed on the edge an hexagonal portlandite crystal (center)-scanning electron microscopy micrograph (secondary electrons mode). Micrograph was captured in a FEI Quanta-Inspect Scanning Electron Microscope coupled with Energy-dispersive X-ray spectroscopy (SEM/EDAX) at the Institute of Nanoscience and Nanotechnology of the National Centre for Scientific Research “Demokritos”