A natural consequence of string theory is a non-commutative structure of space-time on microscopic scales. The existence of a minimal length, and a modification of the effective field theory are two consequences of this space-time non-commutativity. I will first explore some consequences of the modifications of the effective field theory for structure formation in the context of an inflationary cosmology. Then, I will explore the possibility that the existence of a minimal length will lead to a structure formation scenario different from inflation. Specifically, I will discuss recent work on string gas cosmology.