The nodes of a wavelet tree consist of a bit string as well as a character c. In each level of the tree, characters smaller than c are represented as a 0 while character greater or equal to c are represented with a 1. The characters represented by a 0 form the string to be represented by the left subtree while characters represented by a 1 form the string of the right subtree. Therefore, only the bit string of the root node represents all characters while all other nodes represent subsets.