Kusama
Polkadot's experimental development environment.
About
Kusama is an experimental blockchain platform, built on Substrate, that is designed to provide a massively interoperable and scalable framework for developers. It has nearly the same codebase as its "cousin" Polkadot and its made for teams who want to move fast and innovate on Kusama, or prepare for deployment on Polkadot.
For more information, please refer to Kusama web page.