Fidji Simo, the head of Facebook’s app of the same name, said Thursday that she would be leaving the social network to become CEO of Instacart, the on-demand grocery start-up that is preparing to become a publicly traded company become.

Ms. Simo, 35, will replace Apoorva Mehta, 34, founder and CEO of Instacart, with immediate effect. Mr. Mehta becomes Executive Chairman of Instacart.

“I look forward to working with the talented teams at Instacart, as well as our retail partners, to reshape the future of the grocery store,” Ms. Simo said in a statement.

Mr. Mehta said in a statement that he will remain associated with Instacart’s business and “will work with Fidji on long-term and strategic moves that will shape the future of Instacart and our industry for years to come”.

Ms. Simo, the French, spent a decade on Facebook, where she worked her way up from a product marketing position to head of the “big blue app”. Before that, Ms. Simo worked as a strategist at eBay. A graduate of the HEC School of Management in Paris, she joined the board of Instacart earlier this year.

For Instacart, the appointment of Ms. Simo is another step on the way to becoming a possible stock corporation.

Instacart makes money selling subscriptions to its on-demand grocery service and fees associated with it. But the company wants to expand its advertising business with brands that want to advertise their food to customers on the platform. Ms. Simo worked in the advertising business of Facebook and helped develop parts of the company’s mobile advertising.

“We are grateful for Fidji’s incredible leadership over the past decade and wish her all the best in her next endeavor,” said Tom Williams, a Facebook spokesman.

Tom Alison, Product and Engineering Executive at Facebook, will be running the Facebook app on a daily basis until the end of July. CNBC had previously reported on the departure of Ms. Simo from Facebook.