The fashion world recently got a lot cooler. Before his appointment as Artistic Director of Theory last fall, Belgian designer Olivier Theyskens was virtually unknown. The now 34-year-old had stints at fashion houses Nina Ricci and Rochas, but is just now becoming a recognizable name. And for good reason. Transitioning from the luxury world to the contemporary sportswear niche seemed seamless for Theyskens. Celebs and editors applauded his Fall 2011 runway collection, which embraced Theory’s trademark egalitarian simplicity and tailoring, while incorporating an aristocratic feel.

The spring collection can be found at  Neiman Marcus, Barney’s New York, net-a-porter.com and theory.com among specialty retailers. Looks range from soft blouses and dresses, structured jackets and leather pieces, including a jacket worn by Cameron Diaz this month. For fall, Theyskens put his vampy, moody, Victorian aesthetic to work, creating oversized pants, floor-length jackets and intricate dresses and tops.

In theory, Theyskens is the new designer du jour. Except in execution, it’s clear he’s here to stay.

Theysken’s Theory is priced from about $125-$1500.