Picked up a rock that looks suspiciously like a dinosaur fossil? Snapped a photo of a bright blue bird that you can’t identify? Your annual chance to get a world-renowned scientist’s take on it is coming up on September 23 at The Field Museum’s ID Day.

You can bring in clean, dry bones, fossils, rocks, meteorites, seashells, feathers, artifacts, and photographs of mammals, birds, reptiles, fish, and insects—just nothing that’s alive or was recently, or the animals (or their fleas) could get loose in the Museum. And even if you don’t have anything to bring in, stop by anyway—the Museum’s scientists will have specimens on display for you to see (and touch) and are ready to talk shop about your favorite scientific topic. Plus, it's a Free Admission Day for Illinois residents.

The Field Museum is an active research institution that relies heavily upon its 30-million-specimen-strong collections. As a result, it’s “home” to dozens of scientists studying everything from moss to Mosasaurus, and ID Day is the one day every year when visitors can bring in specimens to show these scientists and ask questions about them.

This event marks the Museum’s third annual ID Day. Last year, over a dozen Field Museum scientists specializing in zoology, paleontology, geology, and more were available to identify specimens and answer questions. This year, to meet the popular demand of the event, even more scientists will be on hand.

ID Day will take place from 10 am- 2 pm in on Saturday, September 23 (a Free Day for Illinois residents) at The Field Museum’s main hall (near SUE the T. rex). See you (and your mystery objects) there!

Click here for complete details.