t seems that almost everyone likes treehouses. Smiles of recognition turn into grins of enthusiasm as more people discover them and dream about making their own private retreats or family play spaces. And it's nice to remind ourselves that treehouses are built into the oldest and most forgiving, living things on earth. Also, history records treehouses as being built as deliberate follies, as challenges for arboreal designers, for merrymaking, and for keeping the spirit of fairy tales alive. But treehouses can also be social places. We will visit many that were built to entertain, to hang out with friends, or as guest houses. Trees come in all types.