Lettuce is usually a rather boring part of lunch, but today it was exciting for three astronauts.

Earlier this afternoon, astronauts Scott Kelly, Kjell Lindgren and Kimiya Yui ate red romaine lettuce grown on the International Space station, dressed with oil and vinegar, for lunch.

Since vegetables don't just pop up out of nowhere in space, Nasa started an experiment, called Veg-01, to test the space station's ability to grow food. Now that something has indeed grown, there is hope for future, more substantial crops to feed those on long-duration space missions in the future.

The first crop was planted in May last year and was brought to Earth in October for safety testing. The lettuce eaten today was planted by Kelly on June 8 and grew for 33 days before being harvested. Half of the bounty will be packaged and sent back to Earth for scientific analysis.

The lettuce grew in a rooting "pillow" that contains the seeds and soil for the plants. Before eating, the astronauts had to clean the lettuce with citric-acid based sanitizing wipes.

The Veggie system was developed in Madison, Wisconsin, by Orbital Technologies Corp. and tested at Kennedy Space Center before it took flight. The unit is collapsible and expandable and features a flat panel light bank that includes red, blue and green LEDs for plant growth and crew observation.

Nasa values growing food in space not only for its nutrition, but also as a recreational activity for astronauts during long and grueling missions.