The bubbles in champagne are caused by the release of co2 gas. This gas is produced during the fermentation process, where yeast breaks down the sugars in the grape juice and converts them into alcohol.
As the fermentation procedure continues, the carbon dioxide gas is produced in increasing quantities and ultimately starts to leave from the champagne. This is why champagne needs to be kept in an unique bottle that can hold up against the pressure of the gas.
use this link The abrupt release of pressure causes the carbon dioxide gas to get away from the liquid in the form of bubbles when you open a bottle of champagne. That's why champagne is always served chilled, as this helps to keep the carbon dioxide gas in solution.
Now you understand how champagne gets its bubbles!