Today, Larry Page and Sergey Brin, the co-founders of Google, announced that they would step down from their respective roles in Alphabet Inc., the parent company of the world’s largest search engine. Continuing forward, current Google CEO Sundar Pichai will take the chief executive officer position at Alphabet while retaining his role at Google.

This change comes after four years after Google first announced the new public holding company Alphabet, as well as its own transition from a standalone to a subsidiary of that company. When the change occurred, Page and Brin took the positions of CEO and president at Alphabet, Inc, respectively, while Pichai took the reins at Google.

This new transition reflects Google’s growth in the scale and variety of its ventures and offered services. Page and Brin write, “Today, in 2019, if [Google] was a person, it would be a young adult of 21 and it would be time to leave the roost. While it has been a tremendous privilege to be deeply involved in the day-to-day management of the company for so long, we believe it’s time to assume the role of proud parents,” in a founder’s letter posted today.

This doesn’t mean the co-founders are leaving the company entirely, however. They continue to write, “We are deeply committed to Google and Alphabet for the long term, and will remain actively involved as Board members, shareholders and co-founders. In addition, we plan to continue talking with Sundar regularly, especially on topics we’re passionate about!”

With this change taking place, newly-appointed Alphabet CEO Sundar Pichai’s responsibilities will now include managing Nest, Waymo, Wing, and other subsidiaries that were related to but not directly affiliated with Google.