Google's AI divisions are getting reshuffled, the search giant announced on Wednesday, with chief scientist Jeff Dean leaving the company after 27 years.

Dean, a pioneer in artificial intelligence, is starting his own company, Google said in a blog post on Wednesday. The departure is on friendly terms and Google will invest in his startup, a representative said.

"After an incredible 27-year run, Jeff Dean is at a moment where he wants to try something new, and we're excited to support him in that," Alphabet CEO Sundar Pichai said in a note to staff. "Jeff and Google senior fellow Sanjay Ghemawat are launching an independent public benefit corporation to accelerate discoveries in ML, science, and engineering."

Dean has been credited with some of Google's most important technical breakthroughs dating back to 1999, when he joined the company.

Demis Hassabis, the CEO of Google DeepMind, is moving into a chairman role of that unit. Koray Kavukcuoglu, currently DeepMind CTO and chief AI architect, will take over day-to-day leadership of the AI division and a senior vice president title. He will lead the development of Gemini 4, the company's next major AI model.

"I've decided that now is the right time for me to hand over my day-to-day operational responsibilities at GDM, so that I have the time and space to focus on the big picture and help influence what is to come to the best of my ability," Hassabis said in a note to employees.

He added he would work with Pichai on "strategic and global" matters related to artificial intelligence.