The past three "tallest dog in the world" title holders were Great Danes. Two even had the same colossal name. Here are the world's largest breeds.

Reggie, the tallest dog alive, sniffs the head of Pearl, the world's smallest dog alive. @guinnessworldrecords via Instagram Reggie’s owner, Sam Johnson Reiss, agreed the day was a huge success.

G.G. Goof has spent roughly 275 days growing up at a North Carolina animal shelter after arriving as a puppy.

Guinness World Records shared video from the historic meeting between the world's tallest living dog -- standing 3 feet, 3 inches tall -- and the world's shortest dog, who stands at 3.59 inches tall.

How big is the world's biggest dog ever? Despite Reggie's towering size over Pearl, another four-legged friend holds the record for the tallest dog ever, according to Guinness World Records.

How big is the world's biggest dog ever? Despite Reggie's towering size over Pearl, another four-legged friend holds the record for the tallest dog ever, according to Guinness World Records.