Southern star Tamannaah is making her Bollywood debut with the upcoming commercial flick, Himmatwala, and feels acting in commercial movies is the biggest challenge for heroines. “Commercial films are the biggest challenge for an actor, especially for a heroine because there are limited number of scenes in which that person has to perform. When you are part of a commercial film, conviction is even harder. Different age groups relate to commercial films,” she says. Tamannaah, who has done 27 films down South, says she doesn’t work for fame or stardom. “Even when I was working down south, my main intention was to do good work. Fame and stardom are great, but that’s not the reason I work for,” she says.