One of the most popular course offerings at MIT Sloan is #15.399, the Entrepreneurship Lab (E-Lab), a semester-long course in which students work one day a week in a start-up company. Interdisciplinary teams of MBAs and engineering students are charged with helping to solve a real-world problem that keeps CEOs awake at night. Assignments range from conducting market research for a pre-IPO biotech company, to participating in the creation of a fabless (a company that doesn't manufacture its own silicon wafers) semiconductor company's marketing plan, to helping a software company develop high-level customer profiles. E-Lab students take this extraordinary experience with them as they launch their careers; graduates often return to seek advice, reassess their career options, and replenish themselves from the E-Lab faculty's deep well of insight.