Sam wants a pet for her birthday, but her mom and dad have already said that their apartment is too small for a cat or a dog. A trip to Rainbow Street Shelter to look at the smaller animals can't hurt, though! At the shelter, Sam finds the perfect pet for her, a fluffy black guinea pig named Henry. But she can't help noticing how happy her little brother is when he's reading to Nelly, the Rainbow Street dog. Why can't he read like that when he's in school? Nelly looks happy, too. Sam starts to wonder . . . can a dog go to kindergarten?

Sam chooses a guinea pig named Henry to be her pet, envisions a dog named Nelly visiting and helping her younger brother Liam feel comfortable in his kindergarten class, and encourages Liam to also get a guinea pig as a pet.

Sam chooses a guinea pig named Henry to be her pet, envisions a dog named Nelly visiting and helping her younger brother Liam feel comfortable in his kindergarten class, and encourages Liam to also get a guinea pig as a pet.

Buster isn't fluffy or pretty like other cats—he's a crazy orange cat with attitude. And Mr. Larsen is the exact right person for him. Every morning Buster and Mr. Larsen sit on their porch in the sun, and every morning Josh sees them when he walks to school. When Mr. Larsen goes to the hospital and Buster goes missing, Josh and his family look for that crazy cat everywhere. But if Buster turns up, Rainbow Street Animal Shelter will have to help him find another home. That's when Josh and his family realize that—sometimes—life can choose a pet for you.

Logan is moving from the farm to the city. He'll miss all the things he's leaving behind, but at least he has Bear. He loves Bear more than anything else in the world—because Bear is his dog. Hannah lives in the city. What she wants, more than anything else in the world, is a dog of her own. At the Rainbow Street Shelter, Logan and Hannah find a talking parrot, an old black Labrador, a three-legged goat, a puppy that looks like a peanut—and a Surprise that just might be the best thing in the world.

Stories of ten men and women, from the 1770s to the present, who devoted their lives, and sometimes risked them, to answer some of the big questions in science and medicine.