Semiconducting nanocrystals show light absorption and emission spectrally dependent on their size and shape. Extensive research in the past decades has resulted in numerous wet-chemical synthesis routes yielding nanocrystals with different shapes, accompanied by new properties. For example, pseudo-spherical dots, nanowires and nanoplatelets have been reported with a different number of dimensions in which quantum confinement takes place. The aim of this thesis is to prepare new shapes and compositions of semiconducting cadmium and lead chalcogenide nanocrystals, and to investigate their shape and optical properties with electron microscopy and optical spectroscopy. For example, we study the conversion of CdSe nanoplatelets into quantum rings and reveal their opto-electronical properties. Furthermore, we study the conversion of CdSe NPLs into two-dimensional CdSe-PbSe heterostructures and PbSe nanoplatelets by Pb2+-for-Cd2+ cation exchange, and examine the crystallinity and formation mechanism of PbS nanosheets.