Oprah and Sadie
If there's anything Oprah knows for sure, it's what the love of a dog can do for your life. "There is nothing in the world like puppy love," Oprah says.

Meet her new dog, Sadie!

Still, dogs are more than just companions. They can be the eyes for those who can't see, lead those who can't walk and calm people suffering from conditions like post-traumatic stress disorder.

Where do these service dogs get their start? For some, it all begins behind prison walls...