The aim of this work package is to push the frontiers of optical imaging and biological image analysis to quantify the biological effects of airborne particles on single cells and cell populations from the biological models in Task 2.1, by using high-resolution optical microscopy. The results should enable identification of the key particulate parameters which affect human health and provide new insights into the mechanisms by which aerosol particles disrupt normally healthy cell function. High-resolution optical microscopy will be used to capture the biological effects of aerosol exposure at the subcellular, cellular and cell population levels (Task 3.1). The use of complex, spatially extended model systems poses challenges for many conventional microscopy techniques which are limited in terms of their depth penetration, spatial resolution and imaging speed and often require high levels of illumination causing phototoxic reactions that can lead to spurious cell responses . To overcome these limitations, Task 3.1 will use a combination of cutting-edge high-resolution optical microscopy techniques including super-resolution structured illumination , LSM  and FLIM [27-31] and optical microscopy results will be complemented by electron microscopy images of fixed lung models. Computational image analysis techniques will be developed to quantify the response of the lung models to aerosol exposure and extract unbiased, statistically robust response metrics from the raw image data (Task 3.2). Finally, a pilot imaging intercomparison will be carried out to assess the level of agreement between partners in measuring the biological response of in-vitro models to aerosol exposure (Task 3.3). Task 3.1: Quantitative high-resolution imaging of in-vitro lung models exposed to particulate suspensions The aim of this task is to apply a combination of high-resolution microscopy techniques to capture structural and dynamic image data to characterise the response of in-vitro lung models from Task 2.1 exposed to reference aerosols. Autofluorescence and direct fluorescent labelling will be used to allow visualisation and tracking of aerosol particles for measurement of intracellular uptake. Task 3.2: Image analysis and data processing The aim of this task is to develop computational image analysis tools for the data from Task 3.1 in order to quantify the response of the lung models to aerosol exposure and to track and count aerosol particles. Task 3.3: Imaging intercomparison The aim of this task is to carry out a pilot intercomparison study to assess the level of agreement between partners in measuring the biological response of a model biological systems exposed to reference aerosols.