Tim Cook and Steve Jobs

Cook was Jobs' handpicked successor, and he served as interim CEO during periods when the Apple co-founder was on medical leave from the company. After Jobs died, Cook wrote to Apple employees: "I want you to be confident that Apple is not going to change. I cherish and celebrate Apple's unique principles and values. Steve built a company and culture that is unlike any other in the world and we are going to stay true to that -- it is in our DNA. We are going to continue to make the best products in the world that delight our customers and make our employees incredibly proud of what they do."