The spectrum of the Laplacian operator on a Riemannian manifold M is a discrete set $Spec(M) = {lambda_0 < lambda_1<...}$ that accumulates at infinity. In this talk we will study the smallest positive eigenvalue $\lambda$ of the Laplacian. While it is trivial to put an upper bound on this eigenvalue, we will manage to find a lower bound as well. Amazingly, this bound is in terms of a certain global geometric invariant, essentially the constant in the isoperimetric inequality.