The Department of Molecular Immunology of the University of Groningen (the UG) studies organelle transport processes in immune cells. Upon activation of certain types of immune cells, a reorganization of organelle transport occurs, enabling the cells to secrete large amounts of cytokines and take up antigens. Since some of these processes occur within fractions of a second, a high temporal resolution is required. Furthermore, the UG aims to track these processes throughout the entire cell simultaneously using a widefield microscopy system. To achieve this, the UG has chosen to upgrade an existing Zeiss AxioObserver Z1 microscope available in the Microscopy Facility for frequency-based FLIM. This microscope was chosen for the upgrade because it is highly versatile (fully motorized, climate-controlled, with an extensive range of objectives and fluorescence filters). The UG intends to replace the existing light source and camera or add an additional light source and camera to enable frequency-based FLIM recordings. The UG intends to purchase a light source and camera for installation to enable frequency-based fluorescence-lifetime imaging microscopy (FLIM). The light source and camera must be mountable on a Zeiss AxioObserver Z1, which is already available in the microscopy facility of the Groningen Biomolecular Sciences and Biotechnology Institute (GBB). The setup must be capable of recording images with a frame rate of over 100 fps at a resolution of at least 500 x 500 pixels. The light source must provide pulsed light with at least 3 wavelengths. The camera must be suitable for low-light applications with single photon sensitivity. The camera must have a sufficiently dynamic range to obtain accurate lifetime measurements in cells, where the amount of fluorescently labeled proteins can differ for more than 2 orders of magnitude between different regions within a single cell.