The calcium imaging method allows measurement of responses from neuron populations and is therefore complementary to the single unit recording technique. In our studies, we record calcium fluctuation within distinct glomeruli in the insect antennal lobe, which correspond to the mammalian olfactory bulb. By labelling antennal-lobe output neurons with a calcium sensitive dye we can record their odor-evoked responses. This technique allows to investigate how the primary olfactory center responds to different types of odor stimuli, including both monomolecular components and odor mixtures of different complexity.