Texture analysis and synthesis has been studied extensively by many vision and graphics researchers. A very useful concept in texture analysis is texton or the basic element of a texture image. However, it remains unclear how to define a texton despite the fact that Julesz proposed the term "texton" more than twenty years ago. In this talk, I will propose a two-level statistical model with textons and their distribution for texture analysis and synthesis, with the emphasis on how to define textons computationally. Specically, I will present our recent work on searching for 2D textons in patch-based texture synthesis (ACM ToG, July 2001), 3D textons in Bi-directional texture function (BTF) synthesis (Siggraph'2002) and 1D motion textons in motion texture synthesis (Siggraph'2002).