See-through clothes are officially a trend. Do not confuse this phenomenon with "no clothes," which is popular only with babies and Kesha.
No, we're talking sheer paneling in, say, a black and white dress with a lace bodice on Kristen Stewart, courtesy of German label Talbot Runhof. Tee hee! We can see her sternum!
As for Rihanna—currently being choked to death by one of Donatella Versace's napkin rings—you should know that the dress is a Nini Nguyen and the bathing shorts are by Mack Sennett. Allowing Ri-Ri to flash her calves in a nod to Victorian-era titillation. (My dear Watson, Sherlock Holmes is feeling a mite amorous! Pass the smelling salts, old boy.)
Ooh, the scandal!