Question: what is the last picture a picture of?

Sam Horrell answered on 17 Jun 2013:

The last picture on my profile is the structure of heamoglobin as determined by X-ray crystallography. The protein in blood responsible for transporting oxygen around the body. The picture above the final one is a diffraction pattern from a crystal, the spots represent x-rays that have bounced off electrons in the protien. From those spots we get 3D structures like that one of heamoglobin.