The Soul of Erlang and Elixir [video]
BEAM is such an awesome and beautiful VM. Not only is concurrency at a scale unimaginable in other languages the norm for BEAM, but the isolation of running processes didn't hit me until I asked an Elixir dev about running BEAM in Docker.  The confused look told me I was asking an odd question: processes in BEAM are as isolated from each other as console apps running in different VMs in VMWare server. These processes can send messages to each other but they cannot access each other's memory. It was truly a mind-blowing revelation!