Bubblesphere

When one bubble meets with another, the resulting union is always one of total sharing and compromise

Since bubbles always try to minimize surface area two bubbles will merge to share a common wall. If the bubbles are the same size this wall will be flat. If the bubbles are different sized, the smaller bubble, which always has a higher internal pressure, will bulge into the larger bubble....

Regardless of their relative sizes, the bubbles will meet the common wall at an angle of 120 degrees.