You are looking at ascanning electron microscope image taken by Annie Cavanagh and David McCarthy: a zebra fish larva 32 hours after hatching from its egg.
Zebra fish are one of the fundamental cornerstones of research across fields including cancer, cardiovascular, immune system, infectious diseases and drugs. For example, the zebrafish model for tuberculosis provides fundamental insights into the mechanisms of pathogenesis of mycobacteria. Or that scientists have been able to repair the eyes of rats who have degenerative eye defects by employing stem cells taken from, you guessed it, the zebrafish. They are incredibly useful little critters.
It looks like an alien monster at this scale—but then again, everything looks like an alien monster at this scale, as proven with our old friend Mr. Tardigrade, in the GIF below.