The best salesperson for your product may be someone the world has never heard of.

“A year ago, you needed huge influencers to come in and talk about your brand,” Desiree Gruber told Nina Easton and me on Making a Leader on SiriusXM. "Now you need the micro-influencers or somebody who's got a couple of hundred followers [and is] loyal and loud.”

Gruber, whose company is Full Picture, has never been your ordinary marketer. She helps celebrities (from Kylie Jenner to Heidi Klum to Michelle Obama) and companies (from A&E to Google to Victoria’s Secret) connect with what's hot culturally. While TV once was the main stage to gain fame (Gruber co-created Project Runway for Klum), savvy brand-builders now seek "Instagrammable moments" and validation that is community-based, genuine, and viral.

"Community is at the root of everything," Gruber says. “That's anthropological. We are tribe-driven. We connect with others and hold them close if we like what we feel and what we see.”

So today, “a micro-influencer can sell 700 cups of Starbucks coffee,” Gruber adds. A micro-influencer can also help make a movie a hit, as she and her creative other half (and husband), actor Kyle MacLachlan, explain here.

Listen to this full episode of Making a Leader on SiriusXM Insight channel 121 on Saturday, March 23, at 7 am and 6 pm ET, and Sunday, March 24, at 9 am and 4 pm ET. Pattie Sellers and Nina Easton, partners in SellersEaston Media and senior veterans of Fortune Magazine, host Making a Leader monthly on SiriusXM.