Would you ever tell your adopted child the truth? When and how would you do it?

Studies by social workers have shown that it would be great if parents introduce the word "adoption" as early as possible so that it becomes a comfortable part of a child's vocabulary. Some believe that the best time to tell a child that he or she is adopted between the ages of 2 and 4. Personally, I'd do it around the same age as well. I'd start off my reading children's books about adoption to the child to make him or her comfortable with the idea. This book below is a great example: