WGN News was granted a rare behind-the-scenes look at how a Chicago museum catalogs nature in the city.

WGN’s Patrick Elwood explores the Peggy Notebaert Nature Museum’s Specimen Collection, which includes preserved birds, mammals, plants, fossils, mollusks and more, some of which are over 200 years old.

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“Every one of these in our collection storage area is full of specimens, and every one of these specimens has a little piece of the story that we use to put together the big story of understanding nature and the world around us,” said Dawn Roberts, the museum’s senior director of collections.

Admission is free Thursday for Illinois residents. Click here to learn more.

Watch WGN’s full report in the video player above.