Can I "unsend" a message?

Want to unsend an email message? Add a graphic to an email? How about hiding early morning and evening hours on your calendar? These and many other special functions are previewed in 'Labs' -- Google’s testing ground for experimental features. Warning: Lab features are not as fully tested as the standard features and may cause incompatibilities. Click Settings -> Labs to see a list of recently developed functions, then click Enable to add them to your email or calendar (remember to click 'Save changes' at the bottom of the list).