Eggshells from chicken eggs, seashells, snail shells, and pearls are all primarily made up of the compound Calcium Carbonate (CaCO2). If this compound sounds familiar, that's probably because it is! CaCO2 is the main ingredient in many stomach medicines. It's also even included in many household cleaners.
Unlike in the seashell demonstration (linked to above), a chicken egg won't just completely dissolve in vinegar. Chicken eggs are a bit more complex (for obvious reasons). Instead, we're going to see how, after dissolving the outer eggshell, certain components of the egg are left behind.
Hmm... it seems nobody's added a conclusion for this experiment yet. You can suggest one here.