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 Saturday, Sept. 23rd 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. 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 fourth annual ID Day. ID Day will take place from 10 am- 2 pm in on Saturday, Sept. 23rd (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.