If you are writing a SMS or a mail (or some other text, in other applications) and notice you must go back to edit or correct something, it would be helpful to precisely move the caret back to that point and make your correction, without deleting all text written so far. To do that, tap and hold your finger on the word you want to edit, or somewhere near it; after a couple of seconds a magnifying glass will pop up allowing you to move the caret forth and back one character at a time by dragging your finger.