Caffeine crystals. Coloured scanning electron micrograph (SEM) of anhydrous caffeine crystals (1,3,7-trimethylxanthine). They were produced by a process called sublimation. A liquid containing caffine, such as coffee, is frozen and heated to 238 degrees Celsius, causing the frozen liquid to vaporise without going through the liquid phase. The vapour is then condensed, which drives the water out and results in anhydrous crystals. Some of the crystals have symmetrically intergrown (upper centre, red and yellow). Caffine stimulates the central nervous system (CNS), increasing alertness and deferring fatigue. It occurs in coffee beans and tea leaves. Magnification x400 at 10 centimetres high.
Science Photo Library was founded in 1981 by Michael Marten, one of the authors of "Worlds Within Worlds", a book exploring different ways to observe the universe - from electron micrographs, to images of earthrise taken from the Apollo spacecraft. When Marten started receiving requests for the beautiful images in the book, he had an idea of setting up Science Photo Library.
Since then, Science Photo Library has continued to work alongside world acclaimed photographers and the leading science and medical experts to provide a central source of the best science and specialist imagery available. Although the collection started with scientific images, it has grown to encompass all aspects of science and their impact on everyday life.
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