Nanotechnology is science and engineering at the scale of atoms and molecules. It is the manipulation and use of materials and devices at this level, which is going to create significant impacts on our daily life ranging from fabrication of new construction materials to applications in biomedicine and pharmaceuticals. In this chapter, two areas of applications, namely biotechnology and industrial catalysis, are particularly highlighted. In the biotechnology area, magnetic nanoparticles for drug screening, contrast enhancement agents, magnetic resonance imaging, medicine and bio-separation are focused. Catalysis plays an important role in our society. Presently, over 90% of all industrial chemical productions involve the use of at least one catalytic step. Structure of catalyst used determines how atoms interact on surface. This chapter will demonstrate the use of tailored nanoparticles which offers exciting possibilities for engineering reaction selectivity of catalytic systems of interests at molecular level.