Introduction
Containers enable you to package up your application along with all of the application’s dependencies into a nice self-contained image. You can then use use that image to run your application in containers. Read more at Docker.
The problem is you usually package up a lot more than what you need so you end up with a huge image and therefore huge containers.
A Microcontainer contains only the OS libraries and language dependencies required to run an application and the application itself. Nothing more.
Rather than starting with everything but the kitchen sink, start with the bare minimum and add dependencies on an as needed basis.
See this blog post for a detailed description and comparisons of various ways of packaging: Microcontainers - Tiny, Portable Containers.
Getting Started with Microcontainers
If you're ready to start building your own Microcontainers for your applications, you can use the prebuilt iron/LANG images as a base. They all be found here: https://github.com/iron-io/dockers. And you can see examples of using the iron/LANG images here: https://github.com/iron-io/dockerworker