The Idea: In 1996, Kevin Plank was a 24-year-old former special teams captain at the University of Maryland who hated one specific thing about football practice: the way his cotton t-shirt would turn into a soaked, ten-pound brick by halftime. His compression shorts, on the other hand, stayed bone dry. So he had an idea. What if you made a t-shirt out of the same moisture-wicking synthetic fabric? After graduation, Plank maxed out his credit cards, set up shop in his grandmother's rowhouse in Georgetown, and spent months in New York's garment district sourcing fabric and stitching prototypes. He sent samples to ex-teammates who'd gone on to the NFL, then drove up and down the East Coast with shirts in the trunk of his car, hawking them to anyone in cleats who would listen. This was the beginning of Under Armour.

The Execution:

• 1996: Founds Under Armour out of his grandmother's basement in Washington D.C. and maxes out his credit cards to fund the first prototypes.
• End of 1996: Lands his first team sale - 48 shirts to Georgia Tech for $456 - and closes year one with $17K in total sales out of the trunk of his car.
• 1999: Gets UA shirts featured in the football movie Any Given Sunday and runs a single ESPN The Magazine ad off the back of it. Generates close to $750K in sales.
• 2003: Launches the iconic "Protect This House" TV commercial and takes a $12M investment from Rosewood Capital. The brand officially becomes a household name.
• 2005: Takes Under Armour public on NASDAQ. The stock raises $153M and doubles on its first day of trading - the first U.S. IPO in five years to do so.
• 2010: Crosses $1B in annual revenue just 15 years after starting in his grandmother's basement. Plank signs the shipping box that made the milestone purchase.
• 2024: After stepping down in 2020, returns as CEO to turn the company around.
• 2026: Under Armour is now doing around $5B in annual revenue with a $2.6B market cap, and Plank is worth around $1.1B.

The lesson? You don't need a 10,000 sqft warehouse or a million in seed funding to build a global brand. You need a problem you've personally lived, a prototype in the trunk of your car, and enough conviction to keep cold-calling football teams until one of them finally buys 48 shirts.