My thesis deals with finding counterexamples to Lubin’s Conjecture. Lubin’s Conjecture states that for power series f, g with coefficients in Zp, and f invertible and non-torsion, g non-invertible, then if f ◦ g = g ◦ f , f , g are endomorphisms of a formal group over Zp. This conjecture connects formal power series over the ring of p-adic integers (Zp) to formal groups. In this paper I will explain the properties of Formal Groups, their endomorphisms and logarithms, and will illustrate some properties of power series over the rings Qp and Zp.