Bubble

From Wolfram's MathWorld, a bubble is a minimal-energy surface of the type that is formed by soap film. The simplest bubble is a single sphere, illustrated above by J. M. Sullivan. More complicated forms occur when multiple bubbles are joined together. The simplest example is the double bubble, and beautiful configurations can occur when three or more bubbles are conjoined. An outstanding problem involving a bubble is the determination of the arrangements of bubbles with the smallest surface which enclose and separate n given volumes in space.

While on the subject, a one-bed flat is being marketed in Central London for £3 million or about $6 million. Guests presumably would sleep on a fold-out futon.