Say you edit one photo on your Mac, but forget to update your iPhone and iPad with the newer, more saturated version of that selfie. iOS 8's new Photos app not only lets you access all photos ever taken, but also share edited versions.
This does however eat into your iCloud storage, with some new pricing tiers available. The first 5GB will be free for all users, but if you upgrade to another 20GB, it'll cost 69p a month. Plump up a few quid and you'll get 200GB of storage. Storage options up to a terabyte will be on offer.
From OS X Yosemite to iOS 8, here's everything Apple announced at WWDC