The explosion of available fluorescent probes for cell structure and function offers an unprecedented range of possibilities for the monitoring of cellular activities in real time. Indeed, fluorescence imaging has revolutionized how cell biologists approach the analysis of protein dynamics, patterns of gene expression and even the spatial and temporal dynamics of signaling processes in situ, in the living, functioning cell. These kinds of fluorescence measurements are also highly applicable to

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... onitoring biological function in the spaceflight environment, such as on the International Space Station (ISS). Thus, the resolution offered by such fluorescence-based imaging systems, coupled with the non-invasive nature of their measurements present a powerful approach to following biological responses. Further, the possibilities for remote operation during the experiment and storage of the resulting imaging data for later download and analyses are well suited to the practical limitations imposed on research designs by spaceflight. A driver for wanting to make such measurements is that the ISS provides a unique laboratory where researchers can perform experiments that are impossible on Earth. For example, assessing the biological responses to the long-term exposure to reduced gravity is currently only possible during spaceflight. Yet, such analyses are providing unique insights into how gravity impacts on the biology that evolved on Earth against a constant 1 x gravity.