Most precipitation over continents begins with ice formation in clouds. Biological ice nucleating particles (INPs) probably dominate ice formation at moderate supercooling (> -15 °C), but direct evidence is extremely limited because of experimental challenges related to small INP number concentrations. Here, we propose two novel experiments to solve the issue. One includes three campaigns, four weeks each, at the high-altitude research station Jungfraujoch to sample and analyse cloud droplets and snow, account for riming and analyse normalised differential freezing spectra. The second experiment, including two four-week campaigns in northern Norway, will trace abundance and morphology of INPs from decaying leaf litter through the boundary layer to depositing ice crystals at cloud height. Both experiments have the potential to directly show whether biological particles play a relevant role in cloud ice formation or not.