In 1979, James Dyson had an idea for a new vacuum cleaner — one that didn’t use bags. It took him five years to perfect the design, building more than 5,000 prototypes in his backyard shed. He then tried to convince the big vacuum brands to license his invention, but most wouldn’t even take his calls. Eventually, he started his own company. Today, Dyson is one of the best-selling vacuum brands in the world, and James Dyson is a billionaire. PLUS for our postscript “How You Built That,” how Theresa Stotesbury made a business out of fake blood — a synthetic material that helps create a realistic crime scene for police training.