At Amazon’s annual meeting on Tuesday, company founder and chairman Jeff Bezos confirmed that the online retailer plans to open more physical stores, though he did not put a figure on how many new outlets are to come.

According to the Seattle Times, Bezos told shareholders that operating physical stores is an “experiment.” He then said: “We’re definitely going to open additional stores. How many? We don’t know yet.”

Amazon opened its first physical store, Amazon Books, last November in Seattle. This March, the company confirmed it will open a bookstore in San Diego later this year. A rumor floating around BookExpo America, which took place last week in Chicago, had Amazon opening a store in the San Francisco Bay Area.

Additional store openings was not the only topic covered by Bezos at the annual meeting, though. Talking about Prime, the company’s two-day shipping service (which provides a number of other perks), Bezos said his goal with the program “is to make sure that if you are not a Prime member, you are being irresponsible.” Bezos, as usual, declined to discuss the specific number of Prime members Amazon has, just instead there are currently “tens of millions.”