From 8 to 12 weeks is a very critical time for a puppy to be properly socialized, de-sensitized, handled and potty trained in a positve manor. During this time the puppy is in the fear imprint stage from 8-11 weeks of age wich means it is critical that all these exercises be done in a postive manor and to prevent any tramatic or fearful situations to avoid the imprint that can take months for the puppy to overcome.