Nesting Dolls
A customary of matryoshkas consists of a awkward figure which can be pulled apart to admit another figure of the same likes of inside. It has, in turn, another figure inside, and so on. Traditionally the outer layer is a woman, dressed in a sarafan, holding a rooster. Inside, it contains other figures that may be of both genders, mainly ending in a baby that does not open. The artistry is in the painting of each doll, which can be extremely elaborate.
The onion metaphor is of corresponding character. If you peel the outer layer off an onion, a akin onion exists within the outer layer. This form is employed by designers in applications such as the layering of clothes or the arrangement of tables, where a smaller table sits within a larger table and a yet smaller alone within that. See also onion routing.