GFP...
It's that time of year, when you've got tonnes of stuff to do. Midterms (had my last one yesterday), essays, and finals coming up too soon.
My weekend excitement consists of writing an 8-10 page research essay about the 3D structure of GFP (green fluorescent protein).
This is a 3D view of the protein in a dimer form, showing the atoms, and their temperature (blue means they move very little, and red means they can move a lot).

It's actually a cool (yah, I'm a nerd) protein that takes blue and UV light, and converts it into a fluorescing green colour (the jellyfish in the photo are docotored on computer, they only emit a faint glow in vivo.)
They can attach the protein to other proteins or molecules in the cell, and find out where in the organism that protein is expressed, how it moves, at what concentrations it's expressed etc. Because it's pH sensitive, they can also use it to roughly measure the pH of certain solutions, or cellular environments.