Sourdough starters have become popular items in recent months, with more Americans baking during social distancing. That includes celebrities, as Stephen Colbert found out on Tuesday, April 28.

On the most recent edition of The Late Show with Stephen Colbert, the host talked to actor Jake Gyllenhaal, who was promoting an online event to celebrate legendary composer Stephen Sondheim's 90th birthday.

During their discussion, Gyllenhaal shushed Colbert to reveal that he was working on a sourdough starter.

“I have sourdough rising,” Gyllenhaal said. “It’s resting. My sourdough’s resting.”

“Is that something that sourdough has to do? It has to rest?” Colbert asked in response.

That led to a conversation between the two about the rising trend. The actor explained that he has a friend, Josey Baker, who owns The Mill bakery in San Francisco. Baker taught him how to do a sourdough starter.

Gyllenhaal shared more insight on starters, before he and Colbert moved on to other topics, including the Sondheim celebration.