Jellyfish are especially good models for studying the evolution of embryonic tissue layers. Despite being primitive, jellyfish have a nervous system (stained green here) and musculature (red). Cell nuclei are stained blue. By studying how tissues are distributed in this simple organism, scientists can learn about the evolution of the shapes and features of diverse animals.

This image was part of the Life: Magnified exhibit that ran from June 3, 2014, to January 21, 2015, at Dulles International Airport.