It's a common question at Intermediatheque, where there are so many things to awaken a childlike curiosity - including colorful minerals, ancient Persian necklaces and 19th-century British gear moulds.
The items at Intermediatheque are scientific specimens collected by the University of Tokyo since the Meiji era (1868-1912). These pieces of "intellectual heritage" have been used by researchers in their academic pursuits.
The museum does not have a predetermined route, and its displays have barely any written explanations. Visitors move around as they please, looking for displays that interest them.
Yumika Adachi, 41, of Hatagaya in Shibuya Ward, Tokyo, brought her two daughters, 5-year-old Saya and 3-year-old Suzu, to the museum on a recent day. They were looking at the bill of a mounted bird while discussing the differences between the fish and insects that are the birds' prey.
"They walked over on their own and became so engrossed," Adachi said, pleased with how her daughters were enjoying themselves.
People who want to know more can speak to one of the museum's staff, or do research online or in guidebooks.
Director Yoshiaki Nishino, 63, said the museum tries not to be a place where visitors spend all their time reading explanations and do not pay attention to the displays. "Nothing is more boring than imposed education," he said.
"The purpose of scientific specimens is for research, so there is nothing disagreeable or deliberate about displaying them," he said.
The museum has configured its displays for maximum impact. For instance, inspired by an equestrian statue of Napoleon, a horse skeleton was arranged to stand on its hind legs and neigh.
Some display shelves were old University of Tokyo furniture, making the hall seem like something out of Harry Potter. Inside even such a whisper is audible, creating a dignified atmosphere that brings to mind the museums of 19th-century Europe, a heyday of natural history studies.
However, the museum is actually new, having opened in March 2013. It stands where the old Tokyo Central Post Office used to be, and some of the old post office, built in the modernist style typical of the prewar period, has been preserved.
The museum is a joint project of the University of Tokyo's University Museum and Japan Post Service Co., and occupies about 3,000 square meters on the second and third floors.
While observing the displays, one might glance to see the red brick of Tokyo Station out of the window. On the left are the skyscrapers of the Marunouchi district. Which century was this again?
Address: 2-3F of KITTE, JP Tower, 2-7-2 Marunouchi, Chiyoda Ward, Tokyo
Open: 11 a.m. - 6 p.m. (Thursdays, Fridays until 8 p.m.), closed on Mondays (or the following day if Monday is a holiday)
For more information, call (03) 5777-8600