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. An injured Picard and the children were trapped and isolated in a non-functioning turbolift. 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.