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Image of the Week: Snowflake

25 Dec, 2015

Goodbye Wellcome, it's been fun.

Okay, so it might not be a white Christmas at Wellcome HQ this year, but we rather like this image of a snowflake, captured by light microscopy using modified brightfield illumination before the snowflake melted.

This particular snowflake is from a winter storm in Rochester, New York, and the image was taken by Prof Michael Peres, Professor of Biomedical Photography at the Rochester Institute of Technology. Snowflakes form when water vapour in clouds freezes into ice (rather than when rain freezes, which is better known as sleet). These ice-crystals differ in shape depending on the temperature at which they are created – something like the one pictured above would have formed at around -15 degrees Celsius, while temperatures around -5 degrees lead to columns and slender needle shapes.

Humidity also plays a part in the shaping of snowflakes – the higher the humidity, the more likely they are to have more branched structures. Snowflakes – or “snow crystals” – get their hexagonal base shape from the crystal structure of water, but no-one has figured out why they go from forming plates, to columns, to plates as the temperature drops.

We hope that wherever you are, you are having a warm and cosy Christmas, and we look forward to seeing you all again in the new year.

The Wellcome Trust offices are closed from 24th December 2015 – 3rd January 2016.

Wellcome Images is one of the world’s richest and most unusual collections, with themes ranging from medical and social history to contemporary healthcare and biomedical science. Over 100,000 high resolution images from our historical collections are now free to use under the Creative Commons-Attribution only (CC-BY) licence.

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