Your friend shared an awesome image on Instagram, but it's a bit too small? Unfortunately, Instagram does not let you zoom on iOS. However, Redditor kaidangku suggests you can bypass this by using a built-in setting on your iPhone, iPad or iPod Touch.
The Accessibility settings of iOS include an option to enable Zoom, letting you magnify any screen. Go to Settings > General > Accessibility > Zoom and turn it on. Double-tap the screen with three fingers to zoom in; do that again to zoom it. On the first double tap, you can also pinch out to zoom in more.
The Instagram image gets a little pixellated, but it's still a zoom option where there was none before!