Pure water can only be vitrified by the very slow condensation of vapour on a metal surface maintained at very low temperatures1,2. Attempts to form vitreous ice by rapid cooling of liquid water invariably lead to formation of ice Ih (ref. 3). (Pryde and Jones4 did report a heat capacity change of rapidly cooled water at 126 K which they attributed to a glass transition, but could not reproduce this result in subsequent experiments.) Dilute aqueous solutions in contrast to concentrated aqueous solutions5 behave similarity to water and separate during freezing, even with the highest cooling rates available, into pure ice and concentrated solute6. We report here that macroscopic parts of samples of pure liquid water and of dilute aqueous solutions can be vitrified completely by jet-freezing of micrometre-sized aqueous droplets distributed in n -heptane as an emulsion—the resulting supercooling effect of ∼40 K being essential for vitrification7.