It was the height of the crypto craze in December 2017, and a new cryptocurrency-based game was having its moment. Within about a week of launching, people spent more than $3 million buying digital cats on an Ethereum-based app called CryptoKitties.

But other Ethereum users weren’t having as much fun. The game’s popularity pushed the Ethereum network to capacity, leading to wait times of 24 hours or more for others trying to make transactions on the blockchain network.

That episode led to a realization for many in crypto: Unless Ethereum’s developers made significant changes to its software, it wouldn’t be able to support blockchain-based applications at a scale anywhere near mainstream adoption—the holy grail of many crypto startups. Nearly a year and a half later, dozens of projects have raised billions of dollars from venture capital firms and through crowdsourcing to build blockchain projects that can compete with Ethereum. We profile some of the standouts below.