Google’s head of search is stepping down.

After 15 years helping run Google’s crown jewel search engine, senior vice president and software engineer Amit Singhal said in a blog post on Wednesday that he will leave the company on Feb. 26 to pursue philanthropy.

Much has changed at Google goog since Singhal first joined the once fledging startup. The company restructured itself under the holding company Alphabet, and surpassed Apple aapl as the world’s most valuable business earlier this week. The bulk of Alphabet’s revenue comes from its search engine and related advertising business.

From Singhal’s blog post:

When I started, who would have imagined that in a short period of fifteen years, we would tap a button, ask Google anything and get the answer. Today, it has become second nature to us. My dream Star Trek computer is becoming a reality, and it is far better than what I ever imagined.

Google’s search engine is arguably the ultimate arbiter of the world’s information. Each day, the engine handles billions of searches a day. The company’s prized algorithms essentially train the search engine to provide more accurate results each time a person queries the system.

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Having a top listing in a Google search is extremely important for businesses (including media companies) that rely on Google to steer Internet traffic to their websites. However, when Google alters its algorithms, companies could see their rankings drop, thus negatively impacting their business.

Replacing Singhal is Google’s head of machine learning and artificial intelligence, John Giannandrea. That move signals Google’s increased emphasis on artificial intelligence and its growing importance across the technology industry.

Companies like Apple, IBM ibm , and Facebook fb have been aggressively hiring staff with expertise in cognitive computing technologies that let machines take in information that later help them make decisions similar to humans.

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At Google, Giannandrea helped build the company’s Knowledge Graph that spools factoids from the web relating to a user’s search and bundles them into a little box that appears to the right of the search results.

He was also involved with Google’s self-driving car project, according to a Fortune profile about Giannandrea. Most of Google’s data center computing power is used to make its machine-learning technology work, according to the article.