Apple's biggest event of the year is happening Tuesday — here's everything it's expected to announce

Apple is holding a special event Tuesday where it's expected to announce new iPhones, a new Apple Watch, and more.

The biggest new feature reportedly coming to the new iPhone will be a triple-lens camera that can capture photos with a wider field of view.

We may also learn more about Apple's streaming-TV service that it initially unveiled in March as well as software updates for the iPhone, the Mac, and other products.

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Apple's new iPhone is set to be unveiled this week.

Apple is holding an event Tuesday at the Steve Jobs Theater on its Apple Park campus, where it's expected to make several announcements about coming products — the biggest of which is likely to be the debut of three new iPhones.

Apple is launching its new iPhone — as it has done every September since 2012 — at a time when the smartphone market has been in decline for seven consecutive quarters. With iPhone sales dwindling, the Cupertino, California-based technology giant has increasingly focused on other burgeoning product areas such as its services and wearables division. We're likely to hear more about what Apple has in store for those product categories as well.

Here's everything we're expecting to see from Apple CEO Tim Cook and his crew of execs at the big event, which starts at 10 a.m. PT on Tuesday.