Publisher Summary This chapter focuses on procedural methods that generate new graphical objects by synthesizing geometry. These methods are designed to model the intricate detail found in natural shapes like plants. Procedural geometry synthesis creates an entirely new object by generating its geometry from nothing. The ideas of procedural geometry synthesis extend naturally to procedural scene synthesis and can also be applied to other, nonbiological applications, such as the automatic synthesis of entire cities of unique buildings. The most popular method for describing procedural models of plants and natural shapes is the L-system. The L-system is a grammar of replacement rules that captures various self-similar aspects of biological shape and development. The grammar operates on a set of turtle graphics symbols that translate the words generated by the grammar into graphical objects. The chapter briefly reviews the L-system and turtle graphics and demonstrates them with a few examples. The replacement rules in an L-system that allows it to model self-similar detail can be represented in the scene graph using instancing.