During a winter in which temperatures plummeted to brutally cold levels on several occasions in Europe, photographer Grey Hutton set out with a thermal camera to capture unique images of subjects who lived through the frigid weather – the homeless.

His project, titled Traces of Warmth, features street photos taken from December 2017 through February in London and Berlin, according to PetaPixel. While outside with the loaned thermal camera, Hutton said he experienced temperatures as cold as 1 degree Fahrenheit, but added that his project serves an important purpose.

"I wanted to get closer to these marginalized members of our society and, through their stories and my pictures, offer a new perspective on the realities of living on the streets in the unforgiving environments of Europe's two largest economies," Hutton told PetaPixel.

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(PHOTOS: The Most Unforgettable Images from Winter 2017-18)

In the images above, the thermal camera was able to capture where the highest concentrations of heat were located on these cold nights – not just in the people he photographed, but also in other heat sources, like animals or lights. He posted even more photos from the project to his website, and you can keep up with all of his projects on his Instagram page.

Hutton told PetaPixel it was the first project of its kind to be attempted using the high-definition infrared camera.

"Through their stories, and the striking infrared color palette, I hope to highlight some of the difficulties of sleeping on the streets, and the importance of greater funding for councils to face the growing numbers of rough sleepers, and provide adequate support and housing for those in need," Hutton told PetaPixel.