Apple (NASDAQ:AAPL) is conservatively valued, with a price-to-earnings ratio of just 13. Even more, it could be argued that the market has priced the company for zero net income growth going forward. But does a valuation this conservative make sense in light of continued opportunity for Apple's largest and most profitable business segment?

Apple's iPhone business accounted for 56% of its fiscal 2014 first-quarter revenue, and an even larger portion of is operating profits. As such a large portion of Apple's business, the segment will probably be the biggest driver for Apple stock in the coming years -- even with new product categories on the horizon. Fortunately, several factors point to more growth for the business.

As Fool contributor Daniel Sparks points out in the following video, a growing iPhone business could make the stock undervalued at today's prices.

Daniel Sparks owns shares of Apple. The Motley Fool recommends and owns shares of Apple. Try any of our Foolish newsletter services free for 30 days. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.