Here’s an idea of a soap form called Frugal Soap by designer Ji Woong Kim which aims at the reduction of soap wastage. The soap shape has been designed to have a concave top and a convex bottom. Whenever the original soap gets “used up” and reaches its minimal form, instead of throwing it away it is added to the top concave part of a brand new soap, thus leaving no option for any wastage.

[Yankodesign]