Science isn't all serious - sometimes, people like to have a little bit of fun! And, for this reason, the Technicolor Stickleback was created!
This just in: apparently scientists did this for reasons other than making it look like they used crayon's to color the inside of a fish. Watching the development of different tissue types over time can give us vital information about the way that cells grow and reproduce. Essentially, this teaches us more about life and its origins! (Origins meaning eggs and sperm transforming into people, not molecules transforming into organisms at year zero.)
Since there probably aren't very many fish scientists / human scientists out there, I'll probably need to tell you what the red and blue sections represent. (Don't worry, I didn't know either - that's what the internet is for! Plus kitten videos.)
In this picture, scientists have managed to stain developing cartilage blue and developing bone red. (Which I suppose could be deduced from the ring of blue surrounding the eye of the fish.)
Nature never ceases to amaze, but science often helps us to draw out the beauty of nature. Go science!