Birth to 2 Weeks: Neonatal Period; suckling.
2 Weeks to 3 Weeks: Transitional Period; eyes open.
3 Weeks to 12 Weeks: Socialisation Period; they will startle to sound, at around week 5 will show interest in humans.
12 Weeks to 16 Weeks: Juvenile Period; showing signs of maternal separation and distant exploration.
16 Weeks to 12 Months: Adolescent Period: Growth Spurts and life as a Teenager = Puberty.
12 Months to 4 years: Maturity; if trained properly your dog will become a trustworthy member of your family.