ELI5 Airport Security - why we have a 100ml fluid limit?

Why do we have a limit on the amount of hand carry liquids when we travel, and how is the fluid limit in airports an effective security measure? How was the TSA formed? Are those full body scanners at airports safe?   ... we explain like I'm five Thank you to the r/explainlikeimfive community and in particular the following users whose questions and comments formed the basis of this discussion: thestarkreality, bunjay, mocha-shaka-khan, genxcub, newfocus1964 and xonth To the ELI5 community that has supported us so far, thanks for all your feedback and comments. Join us on Twitter: https://www.twitter.com/eli5ThePodcast/ or send us an e-mail: [email protected]