Costume designer Mark Mariani

The theater world has many unsung heroes: folks such as Mark Mariani who work behind the scenes to make plays look great. A Philadelphia-based costume designer, Mariani designed the costumes for “Freud’s Last Session,” playing at the Mercury Theater, where it made its Midwest premiere in March and runs through June. Created by playwright Mark St. Germain, “Session” centers on legendary psychoanalyst Dr. Sigmund Freud, who invites the rising academic star C. S. Lewis to his home in London.

Mariani comes from Abruzzi and Basilicata roots on his father’s side, and Neapolitan roots on his mother’s side — a fact that matters because the nation that gave the world Armani and Fiorucci instilled a fashion sense in the Mariani family that influences everything that he does today.

Here’s how he explains it: “My parents loved music, classic movies and were very fashionable dressers, so I became a movie buff and knew I wanted to be a costume designer at 16,” says Mariani, now 49. “We were among the very few kids in my city who had our suits custom-made for our graduations, communion and proms. It was important to my father that we be impeccably dressed.”

Mariani’s making a mark in the theater world: He’s a two-time Barrymore Award Nominee for his work on “Dreamgirls” and “Pal Joey,” both of which played at the Prince Music Theater in Philadelphia. While he loves the live stage, he also has his eyes and heart set on movies, as cinema would afford him bigger budgets and increased scope to widen his creative vision.

“I’d love to do more film because you really can be very detailed and have really beautiful, completed looks,” he says. “Sometimes in theater a lot of the details are lost because of [budget] cuts and quick changes.”

On that first point, Mariani is philosophical and most of all positive, no matter how tough things get. “It is a tough business and you never get rich,” he says. “The costume department always gets hit with the first financial cuts and at times that can be a bit overwhelming. But it makes me stronger, pushed me to make fabulous costumes out of nothing at times — and keeps me always wanting to learn everything I can to be the best I can be.”

Mariani takes special pride in knowing that his looks create much of the transformational magic that makes theater such a spellbinding art. “I recently did a 1930s play and the audience went crazy over the costumes,” he says. “For the older patrons, it brought back lost glamour, and for the younger crowd, the costumes were sexy enough to wear today. I add a bit of me in all my designs, so it has a twist or a bit of the awe factor.”

For information on “Freud’s Last Session,” contact the Mercury Theater at 773-325-1700 or visit www.mercurytheaterchicago.com. Tickets range from $45-$55; student tickets are $22 with valid school ID.