Photograph by President Obama's photographer, Pete Souza Pete Souza hide caption

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A snowflake from Kiruna Sweden. Large, well-formed crystals like this one, which is between 2 and 5 mm, usually form when the temperature is around -15 degrees Celsius. A special photo-microscope and colored lights were used to capture the image. Kenneth Libbrecht/Lenart Nilsson Award hide caption

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In October, soldiers with the 101st Airborne Division on patrol in eastern Afghanistan's Kunar province climb the hills and footpaths near the Pakistan border. This volatile border has been a source of constant friction as insurgents pass freely through the mountainous region. David Gilkey/NPR hide caption

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