Russian doll

noun
  1. any of a set of hollow wooden figures, each of which splits in half to contain the next smallest figure, down to the smallestAlso called: matryoshka, matrioshka
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012