Dogs from shelters aren’t usually the first choice when it comes to organizations looking to train service dogs. But I hope one day that can change: Nearly 4 million dogs are euthanized in shelters every year, and many of those are breeds best known for making wonderful service animals—golden retrievers, labs, German shepherds and the like. (But did you know pit bulls and “mutts” make great service dogs, too?) Here’s another factor worth mentioning: Dogs rescued from shelters know what it means firsthand to be abused and neglected, easing that connection with people in need who have found themselves in similar life circumstances.

As animal lovers know, companion animals often surprise us; they melt hearts, break barriers and make miracles. And as you’ll see, the following dogs do just that. Read on to see how these seven smart canines went from shelter dog to service dog—and now dedicate their lives to making this world a better place …