The subject gives an overview of fundamental principles of nanoscience in order to show their importance in the next development of nanotechnologies and related areas. The main effort will be aimed at description of changes of electronic structure given by the quantum mechanical confinement of electrons in nanostructures and of quantum phenomena accompanying transport properties of nanostructures. The consequences of a bigger relative number of surface atoms of nanoparticles (compared to bulk materials) on chemical reactivity, cathalytic effectivity and thermal properties of nanostructures will be discussed as well. Simultaneously, examples of applications of these qualitatively new phenomena covering electronics and spintronics, optoelectronics, as well as sensorics and medicine will be shown.