One example of this that is very prominent in today's media filled society is airbrushing. Many ads found in magazines, especially ones featuring celebrities, have been drastically altered to give the final product an unrealistically perfect look. This is shown in this ad from a couple years ago for the movie King Arthur, starring actress Keira Knightley.
Another example of airbrushing is seen here, with a before and after image of Faith Hill that was on the cover of the magazine Redbook. For the final cover shot, Faith has much a slimmer back and neck area, as well as a very slimmed down arm and stomach. Her skin has been lightened and smoothed, with much work around her eyes and mouth to reduce wrinkles, which are something that occur naturally in many women.