As someone who's spent more late nights with my iPhone than I care ... the grayscale filter can actually improve your experience by making text and icons easier to distinguish.

You can also tap the filter icon next to the search bar to refine ... Filtering your emails on your iPhone or iPad can help ...

Unlock hidden features in the iPhone camera app by tapping on the subject, including adjusting exposure and locking focus while moving the camera. Swipe up or tap the ^ icon in the camera app for ...