Trees and forests are today threatened, even though they could become our best allies. A new look at nature, according to a scientific approach, allows us to lift the veil of appearances and reveal unsuspected particularities of trees. Traditional knowledge then sometimes appears biologically visionary - while, moreover, science discovers phenomena of which even tradition had no idea. This book paints a panorama in which the visible and the invisible intersect. It is about the people of the tree, the secret of the longevity of trees, the golden ratio, new water, tides in the barrels and the cosmic pulse of the buds, subtle messages from the trees, today hui measurable, such as the warning signs of earthquakes, and many other things: what is moonwood? What does an electrodendrogram tell us? How do a wooden house, a wood fire or simply the forest air affect our health? Why have trees and forests been sources of fertility for agriculture and how can they become so again - and thereby act against the greenhouse effect? In many aspects, trees can enrich and inspire us, as long as we integrate them into our actions. Very concretely, they constitute a means not only of mitigation, but also of resolution of the current climate catastrophe. And, much more than we imagine, they can help regenerate humans and make the Earth green again.