Apple now spends 18 times as much on research as it did when it launched the iPhone. These 6 charts show how it became an R&D giant.

Apple has become one of the biggest investors in research and development in the world.It has consistently upped its R&D spending every year for the last 20 years.Lately, it's also been increasing the portion of its revenue it devotes to research.In recent years, under CEO Tim Cook, Apple has quietly ramped up its research-and-development efforts so that it now has one of the best-funded programs in the world.As Cook told shareholders recently at the company's annual meeting, Apple is trying to make some big bets on the future of technology, some of which will pay off while others don't. To that end, company researchers are working on everything from self-driving cars to new computer chips to augmented-reality software and devices.Read this: Apple is now one of the biggest investors in research and development, and critics are wondering what it's getting for its moneyThe company didn't always place such a big emphasis on research. In the past, instead of developing its own technology, Apple was best known for taking technologies developed elsewhere and turning them into polished consumer products.These charts illustrate how Apple's research efforts have changed over the years and how they now compare with those of its corporate peers: