Growth of crystalline ice on atomically flat Pt(111). The temperature and the mean film thickness are indicated. Shown is the relative height of each film, as the absolute height is difficult to assess for the thickest film that does not expose the substrate anymore. Left panel: 2–3 nm (7–10 layers) high, flat-top crystallites appear in the wetting monolayer (dark blue), imaged with an STM. Middle panel: further deposition causes the crystallites to grow laterally and overlap each other (STM). Right panel: a thick ice film that would not conduct sufficient electricity anymore from the substrate to the tip of an STM; an AFM was used instead. More details can be found in Thürmer & Bartelt (2008), Thürmer & Nie (2013), and Thürmer et al. (2014), who also took these data. For comparison, Euclid’s SiC mirrors have a typical surface roughness of 0.9–1.1 nm.