A popular collectible dApp released in 2017. Users could bid on digital cats in the form of ERC-721 tokens. This proved to be one of the first “viral” dApps which rapidly gained popularity. As a result, the Ethereum network quickly became overloaded, as it could not process the transactions that were being conducted, resulting in a backlog and very high fees. This incident displayed the limitations of the Ethereum blockchain and showed that the network would have to scale to meet real-world demand.