Apple Inc. (AAPL)  CEO Tim Cook gave everyone the barest of hints this week about a new area where Apple is placing a big bet.

Speaking with analysts on Tuesday for the second-quarter earnings report, Cook talked excitedly about Apple's plans for autonomous systems, saying the business might extend beyond just vehicles. In June, Cook referred to autonomous vehicles as the "mother of all" artificial intelligence projects, saying they're one of the hardest things to work on. He reiterated that sentiment on the call with investors this week.

"We do have a large project going and are making a big investment in this," Cook said. "The autonomous systems can be used in a variety of ways and a vehicle is only one. There are many different areas of it and I don't want to go any further with that."

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