Puppies are one of nature's greatest wonders and in this brand new two-part series, Puppy Secrets, cameras will follow, in loving detail, four very special litters. From Britain's smallest breed, to one of the most popular, and from working sheepdogs to five rescue pups - breed unknown - cameras will capture their journeys all the way from birth to approaching the end of puppyhood.Viewers will have a privileged look at the rarely seen magic of the early days, through to the moment they move to new homes, and see how puppies form the strongest bond of their lives: not with their mums or their siblings, but with humans.Breeders and carers share their insights, and vet Mark Evans reveals some puppy secrets. It's an eight-week race against time where the pups must hit crucial milestones if they are to be ready to move on…and the clock starts ticking the moment they're born.