A number of teams have signaled their intention to build parachains on Polkadot. Some of these teams are preparing for Polkadot’s launch today by building on the Substrate technology stack.
Polkadot parachains don’t have to be built on Substrate, but they can be and it is easy for them to be used in Polkadot. For Substrate chains to become parachains there is very little technical overhead or extra coding. The chain simpluy needs to bond DOT tokens to lease a parachain slot on the Polkadot protocol and access the global network of blockchains.
This is a rundown of the teams either building on Substrate today or intending to build on Polkadot at launch. Constantly updating.