Easily the most popular personality test in the world, the Myers-Briggs Type Indicator has been harnessed by Fortune 100 companies, universities, hospitals, churches, and the military. But how did it insinuate itself into our jobs, our relationships, and the internet? First conceived in the 1920s by the mother-daughter team of Katherine Briggs and Isabel Briggs Myers, a pair of aspiring novelists and devoted homemakers, the Myers-Briggs was designed to bring the gospel of Carl Jung to the masses. But as Merve Emre recounts in this "brilliant cultural history" (Economist), it would take on a life of its own, becoming an influential and immensely lucrative industry.