Transcript for Mark Kelly Authors Brand-New Children's Book, 'Mousetronaut'
Now, to the new endeavor by astronaut mark kelly, husband of former congresswoman, gabby giffords. Kelly is the author of a brand-new children's book called "mousetronaut." Abbie boudreau talked one-on-one with the former pilot and space commander. Reporter: Commander mark kelly's latest mission. Liftoff. Reporter: A children's book, about this mighty, little mouse. Meteor, the mousetronaut. Kids tend to be interested in astronauts and space, and also animals a little bit. Especially, cute, little mice. Reporter: No real surprise commander kelly came up with the idea in outer space. Mousetronaut, is based on a partially true story. After flying aboard "endeavour" 11 years ago, with 18 mice in a cage. One guy would float around, over to his food. Float over to his water to get a drink. And seemed to really enjoy the experience. Hey, look at what our tiny friend has done, the commander says. He's saved the mission. Reporter: It's about a small mouse, who beats the odds, and saves the day in a big way. This story is really about believing in yourself. Reporter: Believing in yourself. And the power, in this case, of this guy being small. He wasn't the biggest. He wasn't the strongest. But because he did believe in himself. And he was selected for this mission. Reporter: It's a lesson he's reminded of every day. Alongside his wife, former congresswoman, gabby giffords. How is she? Doing really well. Focused on her recovery and therapy. She's getting better every day. Reporter: Commander kelly dedicated the booko his two daughters, who he says always allowed him to reach for the stars. For "good morning america," abbie boudreau, abc news, tucson. Coming up next on "gma," kevin james and henry winkler.
This transcript has been automatically generated and may not be 100% accurate.