1. Specialized Fluid-Filled Sac: Red-eyed treefrog eggs are covered in a sac filled with a specialized hatching fluid. Upon sensing the trigger, typically changes in environmental conditions, this hatching fluid undergoes a rapid chemical change.

2. Rapid Fluid Expansion: The hatching fluid absorbs water and expands dramatically within the sac. This expansion exerts immense pressure on the egg's inner surface, causing the egg to bulge and stretch quickly.

3. Muscle Contractions: Simultaneously, synchronized muscle contractions occur within the embryo's body. These contractions help break the egg's outer shell and facilitate hatching.

4. Hatching: As the hatching fluid expands and the embryo contracts, the egg ruptures, and the embryo is propelled out into the water or onto a nearby leaf. The entire hatching process can happen within a few seconds, allowing the embryos to escape the eggshell quickly.

This synchronized process of fluid expansion and muscle contractions ensures efficient and rapid hatching, providing the red-eyed treefrog embryos with an evolutionary advantage in responding to environmental cues and escaping predators during their vulnerable early stages.