Talking about inside knowledge – when last did you look deep into the microstructure of concrete? At the best of times, concrete as we know it has a smooth, grey and even surface. However, when we inspect it a bit more closely under an electronic microscope, things look a little different. Still grey but anything but smooth and even, the products of cement hydration, the calcium silicate hydrate (CSH) crystals, take the shape of needle-like or plate-like compounds growing into each other to form the structure of the hardened cement paste.