Babies typically start teething around 6 months of age, but it can begin as early as 2 to 3 months or as late as after 12 months. The process usually starts with the two bottom front teeth (central incisors) appearing first. Some babies may be born with one or two teeth or start teething very early, while others may start later than average. Most babies have their full set of primary teeth by the age of 2 to 3 years.