Washington ? Once upon a time there were four little rabbits, and their names were Flopsy, Mopsy, Cotton-tail, and Peter. They lived with their mother in a sandbank, underneath the root of a very big fir tree.

Peter and his friends relocated to the Smithsonian’s National Museum of Natural History Thursday where they celebrated their 100th birthday. To be precise, it was the 100th birthday of the book “The Tale of Peter Rabbit,” celebrated by an exhibition called “Peter Rabbit’s Garden.” It’s devoted to the life and work of British author, artist and naturalist Beatrix Potter.

Peter, standing 6 feet 5 inches and clad in traditional blue waistcoat and khaki capris, welcomed a range of birthday guests, including British Ambassador Christopher Meyer.

“I’m delighted to be reunited again with Peter,” Meyer said.

“It’s been a gap of about 47 years now and he has worn a lot better than I have.”

“Peter Rabbit’s Garden,” the exhibit, is part Peter’s Garden, part Potter’s life.

A narrow corridor with a low ceiling, not unlike farmer McGregor’s infamous gate, funnels into the 5,000-square-foot main exhibit.

There, wall-sized collages depicting Potter’s Victorian childhood flank a full-sized replica of Peter’s sandbank birthplace. A 10-foot-tall overturned flowerpot dwarfs a display of the skeletal remains of birds that Potter, the naturalist, collected.

Film adaptations of Potter’s books play on video and there’s a 360-degree video display of Potter’s Hill Top home in England’s Lake District. Nearby is a gallery of her artwork, including sketches and watercolors.

“If it was just her artwork and not Peter Rabbit, it would be amazing,” said Dennis O’ Connor, the museum’s acting director. “We see this exhibition as a vehicle to introduce people, adults and children, to nature and all its beauty.”

Potter, a serious researcher of fungi, developed a theory of the germination of spores. The scientific establishment of the time rejected it. Today’s naturalists think she was ahead of her time.

“Beatrix Potter was first and foremost a naturalist and she would have been a major scientist had she not been born in Victorian times,” said Linda Leary, author of an upcoming biography of Potter, “Beatrix Potter: A Life in Nature.”

The exhibit runs through May 26.