1. EXTREMOPHILE IMAGES

2. Bacteria that can withstand extreme heat are what cause the vibrant colours around hot springs in Yellowstone National Park in the USA. The water in the geysers and springs at the park can get to temperatures as high as 70ºC. Credit: Steve Ford, Flickr BIGPICTUREEDUCATION.COM Thermophilic bacteria, Yellowstone National Park

3. Thermophilic algae can survive and flourish in extremely high temperatures. The green algae seen here in Yellowstone National Park grows in water at around 50ºC. Credit: Anne Weston, LRI, CRUK, Wellcome Images. Thermophilic algae, Yellowstone National Park

4. Microcystis is a type of bacterial algae that grows in waters with extremely high pH levels, such as Mono Lake in California. The cells are usually found organised into colonies like this and can produce and release harmful toxins. Credit: Specious Reasons, Flickr BIGPICTUREEDUCATION.COM Microcystis

5. These cyanobacteria (bacteria that get their energy from photosynthesis) are endoliths, extremophiles that can survive in extremely rocky terrain. Credit: hawkwing3141, Flickr BIGPICTUREEDUCATION.COM Endolithic bacteria

6. In this aerial view of a salt pond, the microalgae Dunaliella salina, which love extremely salty conditions, create the bright pink colouring. Credit: Steve Jurvetson, Flickr. BIGPICTUREEDUCATION.COM Dunaliella salina, a halophile

7. Honckenya peploides, commonly known as sea sandwort, is a halophile and can grow in extremely salty conditions – most commonly found near the beach. Credit: Bas Kers (NL), Flickr BIGPICTUREEDUCATION.COM Sea sandwort, another halophile

8. Tardigrades, or water bears, are water-dwelling micro-animals that can survive extreme environments. For example, they can withstand extreme low and high temperatures, extreme pressure and doses of radiation that would be lethal for most animals, and they can go without food or water for more than ten years. Credit: Bob Goldstein & Vicky Madden, tardigrades.bio.unc.edu BIGPICTUREEDUCATION.COM Tardigrades from the Goldstein lab, UNC Chapel Hill

9. Certain species of pika, a small rodent found on rocky mountainsides, can live in extreme altitudes. The Himalayan pika, for example, can live at altitudes of up to 4,200 metres. Credit: Philpete, Flickr BIGPICTUREEDUCATION.COM A pika at extreme altitude

10. Reusing our images Images and illustrations All images, unless otherwise indicated, are from Wellcome Images. Contemporary images are free to use for educational purposes (they have a Creative Commons Attribution, Non-commercial, No derivatives licence). Please make sure you credit them as we have done on the site; the format is ‘Creator’s name, Wellcome Images’.Creative Commons Attribution, Non-commercial, No derivatives licence Historical images have a Creative Commons Attribution 4.0 licence: they’re free to use in any way as long as they’re credited to ‘Wellcome Library, London’.Creative Commons Attribution 4.0 licence Flickr images that we have used have a Creative Commons Attribution 4.0 licence, meaning we – and you – are free to use in any way as long as the original owner is credited.Creative Commons Attribution 4.0 licence Cartoon illustrations are © Glen McBeth. We commission Glen to produce these illustrations for ‘Big Picture’. He is happy for teachers and students to use his illustrations in a classroom setting, but for other uses, permission must be sought. We source other images from photo libraries such as Science Photo Library, Corbis and iStock and will acknowledge in an image’s credit if this is the case. We do not hold the rights to these images, so if you would like to reproduce them, you will need to contact the photo library directly. If you’re unsure about whether you can use or republish a piece of content, just get in touch with us at bigpicture@wellcome.ac.uk.bigpicture@wellcome.ac.uk