RailsConf 2016 - Making a Rails App with 140 Characters (or less) by Nate Berkopec - YouTube

Ever felt jealous of "other" Ruby web frameworks whose applications can be run from a single file? Did you know Rails can do this too? Starting from a fresh "rails new" install, we'll gradually delete and pare away to find the beautiful, light, modular and object-oriented web framework underneath. Eventually we'll end up with a tweet-size Rails application! We'll learn about Rails' initialization process and default "stack", and investigate the bare-bones required to get a Rails app up and running.