How to get the sub Branch in a Tree

in a tree, there is a branch. in the branch, there is another subbranch. in the subbranch, there are three leaves: px, py, pz. if i want to fill the px into a histogram, how to write the code to get the subbranch? Thanks.


Please re-review the ROOT User’s Guide for all the possible option. The simplest one istree->Draw("topbranchname.subbranchname.px");