Apple is gearing up to launch its next big iPhone. Except it’s small.

The company is about to announce its iPhone SE. It’s a major announcement for the company, but it’s not the iPhone 7 — that big phone isn’t expected to come out until September.

Instead, Apple will be offering a smaller and cheaper version of the iPhone 6s, according to rumours, all of which will be put into a body with the size and some of the look of the iPhone 5.

But that small phone might be far more important than the big sibling that will follow later in the year. It might even hold the key to the fortunes of the world’s biggest company for years to come.

The iPhone SE comes out at a time of big pressure for Apple: for the first time in years, iPhone sales don’t appear to be growing at their previously super swift speed, and many are worried that a slowdown might be coming. That could be happening for a number of reasons, but it’s certain that at some point Apple will have sold iPhones to everyone who could ever want one.

So if Apple is to keep sales of its flagship product growing, as it must, it will have to look into new markets. The iPhone SE might be the first attempt to do that — the smaller, cheaper phone will let it get some of those people who refuse to upgrade to the bigger handsets, and will let it push further into developing markets like India and China.

But it marks a number of other firsts too, which might make it more interesting as well as more important to Apple. It’s the first iPhone since the very first iPhone not to have a number in its name, for instance, which might be the beginning of a change of strategy across the range.

It’s also not clear how exactly Apple is going to present the new phone. While it’s unclear how many of the newest features it will have, it’s unlikely that it will feature anything that’s not in the iPhone 6s — so Apple will have to find a way to present it on stage to drum up excitement, somehow.

That might involve not actually talking about the phone much, but rather the various other products that are set to be revealed at the event. Or it could choose instead to focus on new software features, and show off how exactly people might use their phone in new ways. Or it might involve an entirely new surprise that hasn’t been leaked at all.

The iPhone SE is going to be a smaller phone. But for Apple it could be the biggest in recent years, and bigger than the iPhone 7.