Haider Ackermann - A tank top becomes an elegant base for evening ensembles in the hands of Haider Ackermann, as this white silk style shows. It's shaped with racer-back straps and a round neck, falls loosely over the body, and is lined with coordinating silk to ensure maximum fluidity. Tuck it into a pair of high-rise trousers to pull focus to the waist of a simple evening edit.