Marissa Flores was one of three children given a tour of the USS Enterprise-D by Captain Jean-Luc Picard in 2368 as a reward for the best science projects at that year's science fair. She was the oldest of the children, but was incredibly shy.
The tour was cut short when the Enterprise-D was severely damaged by a quantum filament. Picard and the children were trapped and isolated in one section of the ship at the time. In an effort to keep the younger children optimistic while they searched for a way out of the damaged section Picard made Marissa his Number One. An emboldened Marissa responded well and helped to get the children to safety.