The last flight of the space shuttle Endeavour will be both manned and squidded.

The most famous science experiment on board, of course, will be the Alpha Magnetic Spectrometer, which will set up shop at the ISS to measure cosmic rays, dusting for the fingerprints of dark matter and antimatter. So that's cool. But is it as cool as baby squid in space?
“The Squids in Space project is a cohesive effort in which the full range of NASA Florida Space Grant Consortium supported categories work together on an experiment destined to fly on what will be the last flight of space shuttle Endeavour,” said Florida Space Grant Consortium Director Jaydeep Mukherjee. “This team, which is composed of Florida colleges and high school students and led by University of Florida PhD research scientist Jamie Foster, will connect the three tiers of education in an experiment studying the effects of microgravity on squid embryos.”
Let me just read that phrase again. "Studying the effects of microgravity on squid embryos." Yeah, that's got to be the coolest thing NASA has ever done.

To be perfectly accurate, though, the project is merely being facilitated by NASA. It's one of several student projects--some from high school and middle school kids!--that have found their home on this mission. (It's especially appropriate, I think, that the Endeavour, the only space shuttle to be named by K-12 schools, is now giving its precious shipboard space to student research projects.)

So, okay, the obvious question: why exactly would you want to put squids in space? I mean, besides the cool factor, what is there to be gained? I did a little more poking around, and, bless the internet, there's a webpage on the project. It turns out that the particular species of squid to be shipped off-planet is our old friend the bobtail squid.
What makes this squid unique is its light organ, which glows at night and hides its shadow from prey lurking underneath. The light is powered by a particular bioluminescent bacteria (Vibrio fishceri) that the squid draws in from the surrounding water. Every day it expels the old bacteria and takes in a new batch. Newly born squid can’t produce the light, but within several hours they become bioluminescent as they take in the bacteria. This development gives scientists a close look at morphogenesis, which is the biological process that causes an organism to develop its shape—one of the fundamentals of development biology. The squid experiment came about when Ned [faculty sponsor] learned about the work of Dr. Jamie S. Foster at the University of Florida in Gainesville. Dr. Foster’s work is focused on what happens to this morphogenesis process under micro-gravity conditions.
A-ha! So the real question is morphogenesis under micro-gravity, or, what is the effect of gravity on how an organism makes its shape? And the squid/bacteria symbiosis happens to be a good model system to answer this question.

If you're having a hard time making that connection, it's because a critical piece of information was omitted from the otherwise excellent summary above. That is, when a newly born squid takes in the bacteria that it needs to produce light, those bacteria induce an serious physical restructuring of the squid's body so that it can host them appropriately. The baby squid actually changes shape as a result of taking in bacteria.

Which is a pretty wild thing to study all by itself, on Earth, but when you decide to study it in space . . . whoa.

Jamie Foster, apparently the inspiration behind the Squids in Space project, has an extremely thorough science website. There I found this very clear, if rather bland, description of the project:
In this research project we examine the effects of microgravity on the normal developmental interactions between an animal host and a bacterial symbiont. To examine the effects of the space environment on animal-microbe symbioses we use the model system between the squid Euprymna scolopes and the luminescent bacterium Vibrio fischeri. . . . a small pilot experiment will be flown on the STS-134 shuttle mission to examine the symbiosis under natural microgravity conditions. Our objectives for this project are as follows: to monitor the normal developmental timeline of symbiosis and examine the host immune response under microgravity conditions.
Hey, hey! Wake up! Did you catch that?