will discuss properties, variations, adaptations and simplifications of Lang’s algorithm for origami design, along with open questions, some of an experimental nature. The input to Lang’s method is a topologically embedded metric tree, from which one has to produce first a convex polygonal region compatible with the tree metric in an “expansive” fashion. Lang’s universal molecule algorithm produces creases that induce a 3D-folded version of the pattern, which may or may not be reachable from the flat state through a continuous deformation. I will start with an expository survey of Lang’s algorithm and results obtained about 10 years ago with John Bowers, continue with some recent answers to older questions and conclude with further new problems.