For some people, shoes are a mere necessity — something you wear so you don't get hookworm. For others, shoes are a prime example of the art of design, a fusion of function and aesthetics, and that's not the Sex in the City crowd we're talking about. For the serious athletic shoe collector, "kicks" link sports and hip-hop, and serve as a status symbol as well. They know the current going rate for a mint pair of any Michael Jordan shoe ever produced and why each one matters (or doesn't). The burgeoning kicks community converges on the Peabody Opera House (1400 Market Street; www.peabodyoperahouse.com) today from noon to 5 p.m. for the Show Me Kicks Expo. They'll be there to buy, sell, trade and discuss the shoes they love. Tickets are $12, and casual fans are welcome.