Some babies start getting their teeth at about 6 months or earlier.  The two bottom front teeth (central incisors) usually erupt first.  Then the two upper central incisors. The rest of the baby teeth come in the next 18 to 24 months.  Not always  in an orderly fashion from front to back.  There are all together 20 teeth that come in.  Between the ages of  2 to 3 years, all of their teeth should be in. See your pediatric dentist for check-ups.