The Biodiversity Heritage Library (BHL) has uploaded more than 150,000 images of biological sketches, some dating back to the 15th century, onto the internet. They’re all in the public domain, and free for anyone who wants them.

The images are pulled from journals, research material, and libraries, altogether more than 55 million pages of literature. BHL is “the world’s largest open access digital library for biodiversity literature and archives,” according to its website. On top of public domain content, BHL also works with rights holders to get permission to make copyrighted materials available under a Creative Commons license.

“To document Earth’s species and understand the complexities of swiftly-changing ecosystems in the midst of a major extinction crisis and widespread climate change, researchers need something that no single library can provide—access to the world’s collective knowledge about biodiversity,” BHL said on its website.

“While natural history books and archives contain information that is critical to studying biodiversity, much of this material is available in only a handful of libraries globally. Scientists have long considered this lack of access to biodiversity literature as a major impediment to the efficiency of scientific research,” the BHL website states.