On August 4, the Polkadot (DOT) project launched a testnet, called “Rococo”, for the implementation of its sharding solutions based on parachains.

• Initially comes with 3 default parachains: Tick, Trick and Track
• Currently supports Horizontal Message Passing, with Cross-Chain Message Passing (which is faster) the long term goal
• Parachains send messages to each other via the relay chain
• Developer can create their own parachains 
• Parachains one of many steps in Polkadot’s goal to establish an interoperability standard