The iOS 10 update adds support for markup on photos. This is something we've seen inside other apps and it is not a brand new idea, but now you can scribble on your photos.
Inside the Photos app there is now a Markup option that is tucked under the three dots for more editing options.
When you are in Messages, you can also choose the photo you want to send, tap on the photo in the send box and then on Markup.
Users can choose what they want to do with options to write, to magnify part of the photo and to add text. If you draw a shape that the phone recognizes it will offer an option to make it into that shape instead of your scribble.
When you save the photo it will save with the markup and you can send that photo in any app.