The Polkadot blockchain is a multi-chain blockchain that is designed to bundle multiple chains together so that they can be executed in parallel. The goal is for every block on the Polkadot blockchain to contain multiple blocks from other chains. This will enable the network to contain the transaction information from multiple chains and dramatically increase the overall interoperability between different blockchain networks. Polkadot was created by the Web3 Foundation, which is led by Gavin Wood, one of the founders of Ethereum. Polkadot is their flagship project, and aims to solve the issues in the blockchain ecosystem related to disjointed governance and interoperability.

Zipper is developing a cross-chain messaging and transaction network. It's powered by the ZIP token. The company is backed by Qtum, OKEX, and other established blockchain companies.

Mixin is a cross-chain payment network for digital assets. Mixin provides a cross-chain solution with built-in smart contracts that facilitates crypto-asset transfers. Developers can also build cross-chain DApps based on Mixin Network protocol.
Mixin also has a messenger that is built on top of their platform and allows users to access their crypto-assets with a phone number and a 6-digit PIN code. Mixin supports Bitcoin, Bitcoin Cash, Litecoin, Ethereum, Ethereum Classic, Ripple, Sia, and plans on adding more.
The network is powered by the XIN token.