The picture above is a 'brainbow' created by a lab in Harvard - it is a fluorescent microscopy image of the hippocampus of a mouse genetically engineered to express three fluorescent proteins. Depending on how the genes of the individual neurones are randomly recombined, each cell will express a different combination of the three proteins, giving each a unique colour! I love the beauty of the resultant image, and it is a great example of the meeting of scientific and aesthetic research that is becoming more and more widespread. Another example is given below - natural fireworks revealed by labelling actin microtubules in dividing cells. These pictures and plenty of others are available in an online exhibition run by the journal Cell at the Cell Picture Show. The images are incredible and there are explanations of what's being shown for those without a biology background - well worth a visit!
Image rights belong to Cell and the original creators.