Since 2007, Apple has been putting out new iPhone models every single year. At this point, the world has gotten its hands on over three dozen unique models that feature different specifications, price tags, and exclusives. Naturally, many of these upgrades have been incremental or not worth mentioning. For this reason, we will be shedding most of these releases to focus on the five biggest milestones in iPhone history.

1 iPhone 4: Front-facing camera

The iPhone 4 from 2010 was arguably the most notable iPhone since the original model's release because it was the first to introduce a front-facing camera. At the time, long before selfies took over the digital world, its primary purpose was enabling FaceTime video calls. However, users eventually started utilizing this lens to take photos of themselves without needing another person's help. Today, many users rely on those front cameras more than the rear-facing ones, and companies continue to improve their output thanks to this popularity.

It wasn't just the FaceTime camera, though; the iPhone 4 introduced the sleek, glass slab design many modern smartphones are known for. Back then, even high-end smartphones were still ugly, as manufacturers were collectively trying to decipher the design formula. The iPhone 4's design was ahead of its time, featuring a premium look that is almost objectively appealing to gaze at. This design did lead to the infamous "Antennagate," wherein users reported dropped calls when they held the phone in their left hand. However, this resulted in Steve Jobs' iconic "You're holding it wrong," and the entertaining memes ensued.

Beyond these changes, the iPhone 4 also featured some notable screen upgrades. Apple introduced the Retina Display on an iPhone for the first time, which featured a 326ppi density that was a significant upgrade from 163ppi. This would remain the default pixel density on iPhones for years to come, including some relatively recent models, like the iPhone XR.

2 iPhone 5s: Touch ID sensor

Three years later, in 2013, Apple launched the iPhone 5s, which featured a Touch ID sensor in the Home button for the very first time. The sensor was wide enough to match a regular fingertip, so users could authenticate by simply covering it with one of their registered fingers. Meanwhile, most Android OEMs were still trying to figure out how to implement any reliable fingerprint scanner. For reference, Samsung didn't include one until the Galaxy S5 launched in 2014. And even then, Samsung's required you to swipe vertically across it for authentication. Apple not only arrived early to the party, but it also offered superior execution.

The iPhone 5s didn't stop there. It also notably packed the A7 chipset, which was Apple's first 64-bit mobile processor. At the time, many perceived that it was overkill for a smartphone. However, Android phone manufacturers eventually followed suit as mobile operating systems continued to advance and offer more demanding features that essentially turned these devices into mini computers.

Apart from Touch ID and the processor boost, the iPhone 5s offered the best, most durable iPhone design to date. It had a minimalist, boxed aluminum body with no camera bump or other irregularities. While it's too small and its thick bezels are unacceptable by today's standards, it still remains a timeless masterpiece that marked the end of the original iPhone's broad design.

3 iPhone 6: Two new sizes

Every end is a new beginning, and with the retirement of the original iPhone design came a new form factor. 2014's iPhone 6 was the thinnest iPhone yet (6.9mm), and it was also the largest. For the very first time, Apple offered customers two iPhone sizes: a regular model and a Plus one. Both were significantly larger than their predecessors, with the former offering a 4.7-inch display and the latter going for 5.5 inches.

Granted, this release wasn't perfect, as this was the series that led to "Bendgate," where the iPhones would bend during use. Still, the lineup normalized larger iPhones, and to this day, Apple continues to offer two size options, catering to as many users as possible.

4 iPhone X: No more physical Home button

The iPhone X launched as the "one more thing" following the iPhone 8's reveal in 2017. It goes without saying that its introduction, which marked the iPhone's 10th birthday, is one of the most notable Apple milestones we've witnessed so far. For the very first time, Apple dropped the physical Home button. The X also gave birth to the infamous notch, which housed the Face ID sensors we rely on today, and it was the first iPhone to support Qi wireless charging (along with the iPhone 8 models). While we now depend on MagSafe charging and the Dynamic Island, the iPhone X undoubtedly laid the groundwork for these technologies.

5 iPhone 14 Pro: Dynamic Island

Lastly, we've got the iPhone 14 Pro, which is arguably the most notable release since the X. Through 2022's Pro iPhones, Apple finally retired the controversial notch in favor of an all-new Dynamic Island that blends software elements with the physical display cutout. It was also the first iPhone to introduce an always-on display that allowed users to glance at timely information without waking their phones. That's not to mention that it offers a major camera boost, bumping the main sensor's resolution from 12MP to 48MP. Sure, the iPhone 14 series wasn't that innovative overall, but it showed that Apple was still ready to try some new things.

Is the iPhone 15 Pro next?

If the rumors turn out to be true, then Apple could finally retire the Lightning port and adopt USB Type-C with the iPhone 15 and iPhone 15 Pro. That's not to mention that it could replace the mute switch that has existed on every single iPhone with a mappable Action button. Additionally, this year's release could mark the end of the boxed stainless steel chassis, as the Cupertino firm could be going for a rounded titanium frame this time around. Taking these potential changes into consideration, it sure seems that this year's premium iPhones will set another milestone. Even if they don't, that doesn't eliminate the potential of the iPhone 16 and beyond.