Optimism, an Ethereum-focused layer-2 scaling solution, has announced that layer-3 chains can now join its Superchain by building on top of the OP Stack.

To facilitate this integration, Optimism has introduced two new features to the OP Stack. Custom gas tokens allow layer-3 chains to design their own transaction fees, and Plasma Mode allows them to choose their individual data availability layers.

In addition, developers who join Optimism's Superchain network will have access to funding, network-wide airdrops, growth campaigns, and an extensive developer network. 

Analyst QuickTake: A layer-3 chain is a network that settles on one of Optimism’s layer-2 chains, such as OP Mainnet, Base, and Mode. Other protocols developing similar layer-3 networks include Arbitrum ( Offchain Labs ) and zkSync ( Matter Labs ).