A set of matryoshkas consists of a wooden figure which separates, top from bottom, to reveal a smaller figure of the same sort inside, which has, in turn, another figure inside of it, and so on. The number of nested figures is traditionally at least five, but can be much more, up to several dozen with sufficiently fine craftsmanship. Modern dolls often yield an odd number of figures but this is not an absolute rule; the original Zvyozdochkin set, for instance, had an even number. The form is approximately cylindrical, with a rounded top for the head, tapering toward the bottom, with little or no protruding features; the dolls have no hands (except those that are painted). Traditionally the outer layer is a woman, dressed in a sarafan. The figures inside may be of either gender; the smallest, innermost doll is typically a baby lathed from a single small piece of wood (and hence non-opening). The artistry is in the painting of each doll, which can be extremely elaborate.

Matryoshka dolls are often designed to follow a particular theme, for instance peasant girls in traditional dress, but the theme can be anything, from fairy tale characters to Soviet leaders.

The word "matryoshka" (матрёшка), literally "Big matron", is a diminutive form of the Russian female first name "Matryona" (Матрёна).

Matryoshkas are also used metaphorically, as a design paradigm, known as the "matryoshka principle" or "nested doll principle". It denotes a recognizable relationship of "object-within-similar-object" that appears in the design of many other natural and man-made objects. Examples include the Matrioshka brain and the Matroska media-container format. The "matryoshka principle" is also an example of Mise-en-abyme. Compare Fractal.
see also : http://russian-crafts.com/nesting-dolls/history.html