When Phoebe Gates and Sophia Kianni set out to build an AI startup, they focused on a challenge they knew intimately: online shopping. The two founders, who met as randomly assigned roommates at Stanford, spent countless hours navigating e-commerce platforms trying to find the perfect wardrobe additions. That frustration sparked an idea—what if AI could help people discover, shop for, and buy items more intelligently? At TechCrunch Disrupt 2025, Gates shared on stage that the core question driving their work was simple: “Why doesn’t everyone have a personal shopper in their pocket?” The answer, they believed, lay in AI. Phia began as a class project that quickly revealed strong early demand. But the team didn’t rush to launch. Instead, they spent time refining the product until they found the right product-market fit, according to Kianni. The result is a tool available as a browser extension and mobile app that helps shoppers compare prices across more than 150 second-hand marketplaces. It also includes a vast in-house database of over 350 million items, making it easier to find and evaluate options. A key differentiator is its focus on sustainability—Kianni noted that buying second-hand can reduce a product’s carbon footprint by up to 80% compared to purchasing new, while also offering significant cost savings. The platform also helps users understand the long-term value of their purchases. “If you’re looking at a $500 handbag, can you resell it for $300 or $400? Or, if it’s a fast-fashion piece you’re buying for $100, is it only going to resell for $10? Does it lose 90% of its value the moment you buy it?” Kianni explained. Phia is now developing an AI shopping advisor that will go beyond price comparisons. The feature will assess whether an item is a good deal, predict its future resale value, and even offer personalized sizing insights based on a user’s past orders and returns. This sizing tool is currently in beta with a select group of users. To build awareness, the founders have used a mix of creative strategies. They launched an ambassador program, created original content about the product’s evolution, and even started a podcast. “The ability to gain hundreds of thousands of downloads at a very low cost through the podcast and other distribution channels has been crucial,” Kianni said. Gates emphasized that authenticity played a big role in their success. “There was a bit of an ego death we had to go through,” she admitted. “At first, I wanted to look perfect in every video. But to truly connect with people and produce content at scale, you have to pull back the curtain.” Gates, whose father is Bill Gates, acknowledged her privilege but noted that her background doesn’t always translate into practical startup advice. “My dad is a genius, but he’s not the one shopping on Phia,” she said with a laugh. “He’s not comparing deals across sites or planning his spring break wardrobe. He’s not the user.” That realization helped the team stay grounded and focused on their actual customers.