Prior to iOS 6, the process of emailing a photo required you to start in the Photos application and email the photo from there. You couldn’t do it from within the Mail application. iOS 6 changes this.
When composing an email on your iPhone/iPad/iPod touch, double tap in the body of the message. The familiar option bar (Select | Select All | Paste, etc.) will appear. A new choice has been added – Insert Photo or Video. (On the iPhone/iPod, tap on the arrow on the far right of the option bar to get to this option.)
Tap on Insert Photo or Video and you’ll be taken to Photos. Select the photo or video you want to attach. Repeat this step if you want to attach more than one photo or video.