Classically, cellular signalling is investigated measuring different optical or elec. properties of either single cells or microliter vols. of suspensions of live cells. Here we show how ligand binding to cell surface receptors and subsequent signalling reactions can be monitored in single submicrometer sized vesicles derived from biol. cells. These vesicles are the smallest autonomous containers capable of performing cellular signaling reactions, thus opening the door to downscale anal. of cellular functions to the micro-/nm and femto-/aL range. We describe a method that allows the massively parallel isolation of attoliter exptl. vols. and their self-assembled positioning with 100-nm precision in ordered arrays on surfaces. This miniaturization opens novel routes in functional proteomics such as multiplexing single cell bioanalytics or investigating receptor mediated signalling in multiarray format. Single mol. spectroscopies of suitably labeled proteins are used to investigate ionotropic receptor and GPCR mediated signalling in this miniaturized format. [on SciFinder (R)]