Abstract: Let Q be a directed quiver. The exceptional kQ-modules are by definition the indecomposables without self-extensions, or, equivalently, the indecomposable direct summands of tilting modules. It is known for a long time that exceptional modules are tree modules. The aim of the lecture will be to outline a convenient procedure for obtaining a tree basis for an exceptional module. The proof will rely on the structure of the preprojective (or preinjective) representations of the infinite regular trees with bipartite orientation.