Jeff Dean, Google's 30th employee and chief scientist, is leaving after 27 years to co-found AI startup Discovery Loop, a public benefit corporation, with Sanjay Ghemawat, Oriol Vinyals and Quoc Le. His last day is Thursday, August 6. Dean joined in 1999, when the company had 25 employees, and leaves it at 190,000-plus. In his farewell note, he mentioned scaling Google Search's index 100X, starting the TPU program, changing offices 18 times, and that a Google badge gets a cappuccino in more than 100 cities. CEO Sundar Pichai said Dean and Ghemawat drove some of Google's most significant technology transitions, from early search infrastructure to neural networks, and that Google will keep collaborating with the new startup as a founding investor and Cloud partner. Dean wrote the first Ads system, helped launch News and Translate, and with Ghemawat designed MapReduce, BigTable and Spanner. They are the only Google employees ever named senior fellow. In 2011, Dean built Google Brain, whose early hires included Le and Vinyals. After ChatGPT landed in late 2022, Google folded Brain into DeepMind, and Dean and Vinyals were put on Gemini. Discovery Loop aims to build AI that improves itself with little human input, targeting chip design, drug discovery and materials science. Seed funding comes from Radical Ventures, Khosla Ventures and