Ethereum

In 2013, a precocious teenager named Vitalik Buterin saw the rise of Bitcoin and decided to expand on the cryptocurrency's vision of decentralization. While Bitcoin was a decentralized ledger for sending and receiving currency, Buterin thought of Ethereum as a decentralized computer to run software. 

One year later, Buterin and a team of cofounders raised $18 million for Ethereum in an initial coin offering, or ICO, setting off a wave of ICOs for new cryptocurrencies. (None would fare as well as Ethereum.) Ethereum's token is currently the second-largest worldwide, behind only Bitcoin.

More than a decade later, Buterin's vision for a "world computer" has arguably come to pass. Ethereum houses several financial applications, and a network of layer-2 blockchains built atop Ethereum hold billions of dollars in value. Still, not all investors are thrilled with the protocol. As Ethereum faces competition from a slew of upstart crypto networks, the Ethereum token has yet to substantially surpass its price from 2021.