Babies can begin to teethe as early as just a few months old, but it might take a while before the actual tooth even appears. Some babies never show any signs of teething apart from drooling and chewing on everything. Others will get fussy and cranky as the tooth is popping through. Some babies will sleep through it all while others will have numerous night wakings. Some experts have said it will not disrupt sleep, but I wholeheartedly disagree. As with everything else, all babies are different