Electrospinning is becoming an increasingly popular method for producing polymer fibers, since it can attain microscale to nanoscale control of fiber dimensions, morphology, and functionality. Hence electropun fiber technology is now prevalent in numerous applications ranging from tissue engineering, active filtration systems, and super strong materials design. The electrospinning technique has attracted much attention in its biomedical applications in recent years, such as preparation of scaffolds for tissue engineering applications. Here we present a systematic study of the manner in which the cells interact with electrospun scaffolds and the effects of the scaffolds have on basic cell functions, such as morphology, proliferation, and migration. We obtained electrospun polymer fibers of different diameters, ranging from hundreds of nanometers to several micrometers. Furthermore, we aligned the fibers and formed multilayered structures where both the fiber spacing and pore size could be varied. We found that cells preferred to oriented along the fiber axis when the fiber diameter was above 1 micrometer. Cell measurement on the other hand, indicated that the proliferation on the aligned fibers was more efficient than the flat surface since the oriented cells did not become confluent as quick as on the polymer thin film. The average migration velocity of the cells on the aligned fibrous scaffold, was lower than that on the planar surface, but remained constant in time.Efficient filtration of ions and very small particles often requires small pores which restrict the liquid flow and consumes large amounts of energy. Here we show that electrospun fibers can be used to create an active filter, with nearly unrestricted flow. We addressed the use of electrospun fibers to encapsulate microbes of industrially relevant genera. Although the electrospinning typically uses harsh organic solvents and extreme conditions that generally are harmful to bacteria, we describe techniques that overcome these limitations. The encapsulated microbes were viable for up to several months, and the exchange of nutrient between the microbes and their environment was not affected by immobilization. Since polymeric chains have multiple degrees of freedom, confinement alone can impart special properties. For example, in semicrystalline polymers, which constitute the largest group of commercially useful polymers, confinement can change the melting point while at the same time improving the mechanical properties. My last area of research therefore includes the confinement effects brought by electrospinning semicrystalline polymers into very thin fibers, and the impact of viscosity and nano-additives such as clay. In this chapter I will try to explain these effects by introducing a model based on the viscosity properties of the elelctrospinning solutions.