As a new opportunity similar to DeFi or NFT, we are eagerly looking out for new innovative ideas from Blockchain applications.
And recently, Avalanche announced
Subnets! But what are Subnets?
Subnets are unique Blockchains on Avalanche, where people will be able to create own Blockchains based on Avalanche Coins. Just like people can create an Ethereum Token, Subnets on Avalanche are for a whole Blockchain, deriving from Avalanche's Coin. It's Token 2.0 economy and could be huge, when coders can take advantage from it.

Many coins will be used for buliding such applications.
Here is a detailed and technical Article from Avalanche developers, why Subnets are likely to bring a new opportunity like DeFi and NFT’s did:
https://medium.com/@demirelo/the-era-of-avalanche-subnets-9e94f377cb65