He got his start working as a cartoon and graphics artist for several advertising agencies and small studios in Athens and later pursued his studies in art and animation in the United States.
A year later he joined the newly founded DreamWorks, Character Builders where he worked closely with Steve Hickner, director of Prince of Egypt, with whom he formed a friendship.
Between 1998 and 2000 at DreamWorks, Nassos completed Joseph: King of Dreams and storyboards for the films Outlaws, Tusker, Tortoise and Hare and the acclaimed Spirit: Stallion of the Cimarron.
At the end of the 90s, during a professional trip to London, Nassos met Panagiotis Rappas, another Greek animation artist and owner of Stardust studios.
Together, they founded Time-Lapse Pictures LLC and signed a deal with Klasky Csupo for the production of the Paramount release Rugrats in Paris: The Movie.
During 2007-2009 Nassos and Time-Lapse PIctures co-produced the animated Christmas specials " The Little Mouse That Wanted to Touch a Star" and "The Boy and the Tree" based on a short stories by Eugene Trivizas. "