Among the other features Apple highlighted today is extensibility through app extensions, which allows different apps to “project” their interfaces into other apps. This is handled through a sandbox to ensure safety. With this, you can link your photo-editing app to Mail, for example, and then easily move between Mail and the photo-editing app. This also gives Safari access to extensions. Apple’s Craig Federighi, for example, demoed translations through Bing Translate right in Safari.