Weeks after Apple's  50th anniversary, the US technology  titan announced on Monday that its CEO Tim Cook would step down in September, to be succeeded by hardware engineer John Ternus. Ternus will step into some of the biggest shoes in corporate America. Cook is credited with turning Apple from a $350 billion (€298 billion) company when he started to a valuation of over $4 trillion today. Ternus takes over a tech giant that must keep its premium edge — the iPhone  recently  retook the crown as