Clouds are essential for the Earths climate system, weather phenomena, and the hydrological cycle. Cloud microphysics determine cloud albedo in the visible and infrared spectral ranges, cloud lifetime, and precipitation properties. In all these processes, aerosol particles play a crucial role. They can act as so-called cloud condensation nuclei for liquid droplets and as ice nuclei for the formation of ice particles. Ice nuclei catalyze the freezing process in clouds and support the kinetically hindered phase transition from water to ice, which is called heterogeneous ice nucleation. Several materials can act as ice nuclei, such as carbonaceous residues like soot, biological materials like pollen or bacteria, and mineral dusts like albite or microcline. Even though intensive research on ice nucleation has already been performed for decades, the mechanisms during the freezing process remain still fragmentary. This is, among other reasons, due to the tremendous variability as well as complexity of ice nuclei. The goal of this study was to obtain a fundamental understanding of physical and chemical processes during ice nucleation, by conducting a comprehensive study of the ice nucleation behavior of artificial droplets including ice nuclei. The current technique to determine the ice nucleating behavior of aqueous droplets in micrometer range was optimized regarding the formation of droplets with defined diameters between 20 m and 80 m, process control and experimental evaluation. In addition, carbonaceous ice nuclei as graphene, soot or cellulose have been investigated concerning their properties as ice nuclei. Complementary analysis techniques to determine the particles chemical and physical properties have been performed. Detailed investigations by cryo- and electron microscopy, as well as Raman- and X-ray photoelectron spectroscopy, revealed the influence of the chemical composition and crystal structure on ice nucleating properties. This study demonstrates the absolute need for a thorough analysis of the entirety of physical and chemical properties of carbonaceous particles in order to draw conclusions concerning their ice nucleation activity.