The idea was simple: to let anyone tag along on what the couple invested in privately.
Sebastian founded the digital bank Klarna in 2005 and has spent the past 20 years building it into one of the world's most successful fintech companies. In 2025, Klarna listed in New York – making it one of the largest Swedish public companies founded in the 21st century.
Through Klarna, Sebastian has built close relationships with leading entrepreneurs, investors and executives globally — and gained insight into global growth companies that few can match.
Nina Siemiatkowski went from global head of marketing to entrepreneur in 2018, when she founded Milkywire — an impact company that helps businesses turn climate and nature ambitions into concrete investments and real change. Today, Milkywire is an internationally leading player in climate and nature investments. Nina is also the founder of the Siemiatkowski Foundation, a non-profit focused on protecting ecosystems.
Entrepreneurship runs through everything Flat does, in our investments and in how we operate. It's a belief in the founder, that nothing is impossible, and in the value of moving fast. And family control means the long term. We hold on our own timeline.
