Trees are incredible living beings. With their roots deep in the earth, branches high in the sky, and with leaves straight to the sunlight, they stand there for decades and centuries on the same location. They are real living estates. (In German its called "Immobilien" it means not mobile) Can we learn from trees how to build houses? Can we grow houses out of trees? Yes, or better probably, because the mainstream habits are difficult to satisfy in living rooms. We must adapt a bit to the trees if we want to live with, on or in them.