The most challenging age for a puppy is up to 18 months. During this time, puppies undergo several physical and mental changes that can be rewarding and exasperating for puppy owners. During this time frame, puppies must learn basic commands, potty training, and behaviors that become vital to their relationship with humans. Additionally, they are going through teething, which involves a lot of chewing! This means pup owners must be attentive to ensure the puppy only cheats appropriate objects and provides plenty of chewy toys or bones to help soothe their gums.