`aio` is to Emacs Lisp as [`asyncio`][asyncio] is to Python. This package builds upon Emacs 25 generators to provide functions that pause while they wait on asynchronous events. They do not block any thread while paused. The main components of this package are `aio-defun' / `aio-lambda' to define async function, and `aio-await' to pause these functions while they wait on asynchronous events. When an asynchronous function is paused, the main thread is not blocked. It is no more or less powerful than callbacks, but is nicer to use. This is implementation is based on Emacs 25 generators, and asynchronous functions are actually iterators in disguise, operated as stackless, asymmetric coroutines.