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Fans pose during the Lollapalooza Berlin music festival on September 10, 2017 in Dahlwitz-Hoppegarten, Germany.
You can bet most millennials have heard of Snapchat, emojis, AirPods, and Drake.
But sea monkeys, Brownie cameras, milk chutes, and Ricky Nelson?
Not so much.
The Pew Research Center defines millennials as those who are between 20 and 36 years old in 2017, on the cusp of Generation X (and including the youngest "Xennials") and followed by Generation Z. They're the largest generation so far, and they influence everything from fashion trends to office layouts.
But they don't know everything.
Below, find 17 things that for many people are fond memories - but for millennials, they're almost unheard of.