Google has always had a love-hate relationship with advertising. Its power and wealth come from the $16 billion a year of advertising that it sells. Yet on its most important pages, the results from its Web search engine, it has limited ads to nothing more garish than a dozen words of text.That is about to change. On Thursday, Google started testing video ads on some pages of search results. And it is developing ad formats with images, interactive maps and other more elaborate features.

Marissa Mayer, Google’s vice president of search products and user experience, said in an interview that the change reflects the evolution of the once-sparse Google pages. Last year Google introduced what it calls universal search, which mixes images, videos, news stories and other types of information with the standard text links to Web pages.

“The big insight of Google wasn’t text ads; it was that the ads should be conducive to the format,” Ms. Mayer said. “We were doing text-based search that was all textual. Visual ads don’t work in that format.”

By contrast, she said text ads are not as effective on pages with search results that include images and video. The eyes of users automatically gravitate to the images more than the text, she said. Now that Google’s main search results pages include more images, video links and other elements, it is more appropriate, she argued, to have corresponding advertising formats.

“With universal search, something is getting shaken up a bit on the bottom part of the page,” she said. “The ads on the top part of the page should match.”

At first, users will barely notice the change because the videos will not be immediately obvious. Ads with accompanying videos will have a small button with a plus sign. Google has increasingly used the plus icon to indicate that certain information — like a map — can pop up on a search results page. Users that click the plus button on an ad will see a small video player that shows a commercial, movie trailer or other clip.

Ms. Mayer said, however, that the company would explore adding small thumbnail photos to the video ads as well. And a spokesman said the company is considering testing other formats that may include ads with images. But it is taking a delicate approach.

“We don’t want all sorts of video and banner ads all over the site all the time,” Ms. Mayer said. “People who advertise a movie want to show a trailer. Why shouldn’t they have the same format we use for search results and have a little plus box that says watch the trailer?”

For now, advertisers will not pay extra to put video in the ads. They enter a price they will pay for a click in Google’s regular text-ad auction. But in the video ads, the advertiser pays when users click to see the video, even if they never click through to the advertiser’s site.

This allows Google to expand what it can offer advertisers that are focused on promoting their brands, rather than driving traffic to a Web site. But Ms. Mayer said the company was not changing its idea that ads need to be directly relevant to what users are searching for.

“If you search for golf clubs, you get ads for golf clubs, not a banner ad about Pepsi that you may drink on the golf course,” Ms. Mayer said.

As always on Google, ads are shown based on a combination of factors, including the amount bid and how often they are clicked on.

Google, which owns YouTube, the largest user-contributed video site on the Web, has been exploring a wide range of ways to put video ads online. It started selling video ads that could appear on other Web sites two years ago.

The test is scheduled to begin today in a small fraction of Google searches. Google would not provide an image of what they look like. If you see one, grab an image and send it in to bitsfeedback (at)