In late 2013, Vitalik Buterin described his idea in a white paper, which he sent out to a few of his friends, who in turn sent it out further. As a result, about 30 people reached out to Vitalik to discuss the concept. He was waiting for critical reviews and people pointing out critical mistakes in the concept, but it never happened.
The project was publicly announced in January 2014, with the core team consisting of Vitalik Buterin, Mihai Alisie, Anthony Di Iorio, Charles Hoskinson, Joe Lubin and Gavin Wood. Buterin also presented Ethereum on stage at a Bitcoin conference in Miami, and just a few months later the team decided to hold a crowdsale of Ether, the native token of the network, to fund the development.