Milky Way Galaxy models
The Milky Way structure, in particular the spiral arm design is not easy to determine due to our location inside it. Indeed, near/far distance ambiguity and streaming motions make difficult the distance determination of the arm tracers. In this context I am going to review and discuss the methods to find the number and the design of the arms of our Galaxy. In a second step I will review some modeling aspects which could help us to understand its structure.