I had to copy this tweet from the Lund Vision Group because the photo is so amazing! It’s a mantis shrimp developing in an egg. You can see the compound eye developing (the browny part over the yellow yolk). Getting a better understanding of the development of the stomatopod eye would be fascinating since their vision is so complex. If you don’t already know, stomatopods have up to 20 photoreceptors and can detect UV, visible, linearly polarised and circularly polarised light.
If you’re interested in more amazing mantis shrimp photos, check out Dr Michael Bok’s webpage.