NestTree

NestTree[f,tree] adds children to each leaf of tree, with f[expr] giving the list of data for the new children of a leaf with data expr.

NestTree[f,tree,n] successively applies f to the data of each leaf up to level n, adding at most n levels to each leaf.

NestTree[f,tree,n,h] additionally applies h to the data of the new subtrees.

NestTree[f,expr,…] constructs a tree by nesting f on the tree leaf with data expr.

Examples

NestTree[{#-1, #+1}&, 0, 2]
(* Creates a tree starting from 0 with two levels *)

Please visit the official Wolfram Language Reference for more details.