Academy scientists travel all over the world and bring what they find back to San Francisco.
So, in addition to all of the creatures visitors see on exhibit, there are even more behind the scenes.
There are an estimated 2.5 million other fishes at the Academy that most people never get to see.
"Scientists see them," senior scientist John McCosker said. "Scientists come and visit; we send them in the mail."
The collection is a sort of dictionary of biology, with records of species collected more than 100 years ago. The collection ranges from extinct butterflies to stunning birds.
The racks and drawers fill an entire side of the new building. Every one of the 20 million speciems was moved out the old Academy to a temporary storage area, then into the new building.
"Didn't drop a jar, didn't lose a fish," McCosker said. "The move went very well."
McCosker showed ABC7 around the collection. His favorite specimens are from the deep sea.
"Like this Ramora," McCosker said. "I mean, what a strange looking creature. It looks like road kill, but in fact what it is an adaptation for attaching to whales and sharks and turtles."
Another of McCosker's favorites is the angler fish.
"In the deep sea, it's all dark except for the little light on the end of his fishing lure which is bioluminescent, so it has a little light bulb at the end of his fishing lure - and it's wiggling like that, so if something comes up to investigate - it just grabs it and swallows it," he said.
The deep sea angler McCosker showed ABC7 is a close relation to the frog fish living in the aquarium, and the two demonstrate part of the beauty of having all of the specimens together at the Academy.
"What is this species, what's it related to, what is its role in the eco system, why did it go extinct," McCosker said. "Things like that can be learned from this library of science that we maintain here."
Written and prodeuced by Jennifer Olney