"The unavoidable limitations of further miniaturization of electronic circuits stimulate the search for new information and storage technologies. Spintronics is one of the major new directions that emerged in recent years - it aims at using the additional degree of freedom, namely the spin, to store and process information. One of the most promising candidates for future spintronics devices are nanostructures such as molecules and quantum dots. However, in order to exploit such devices in spin nanolelectronics, it is crucial to fully understand their behaviour and properties. The main objective of this research project is to gain further insight into spin-resolved transport properties of complex quantum dot and molecular structures coupled to leads exhibiting either ferromagnetic or superconducting correlations. The emphasis will be put on the strong coupling regime, where electronic correlations lead to the Kondo effect. In particular, the considerations will include the analysis of the SU(4) Kondo effect in double quantum dots and carbon nanotube dots and thermoelectric effects in spin-resolved transport through Kondo quantum dots and molecules. The transport characteristics of hybrid quantum dots, in which one of the leads is ferromagnetic while the other one is superconducting, will be also considered. All these nanostructures have become particularly interesting in view of recent experiments. The calculation of transport properties will be performed by using the numerical renormalization group methods with state-of-the-art improvements – these are known as the most powerful and exact methods to address transport through quantum dot and molecular systems. The results obtained will provide new insight and understanding of current and future experiments on transport through various magnetic nanostructures in the Kondo regime. They will be also published in refereed scientific journals and presented at international conferences and workshops."