Microbial ecology deals with interactions among microorganisms, between microorganisms and their environment, and with water relations in the microhabitat. In the desiccated state, many lichens tolerate long periods of intense stress. The present report describes the use of scanning electron microscopy with backscattered electron imaging (SEM-BSE) to observe - on the spatial nanometer scale - relationships among the epilithic thallus of an Antarctic lichen, microorganisms belonging to epilithic, chasmoendolithic and cryptoen- dolithic communities and minerals. The main aim of the study was to determine the precise location of minute quantities of water that the thallus may maintain probably obtained from the mineral microenvironment of its rock habitat. Through low temperature scanning electron microscopy (LTSEM), it was possible to observe ice crystals indicative of the presence of water in the dehydrated hyphae of the fungal partner of the lichen when these were cross- fractured. Ice crystals were also detected among the mineral particles of the lithic substrate. Besides implications in the highly controversial topic of water distribution in the lichen thallus, the present findings suggest that under conditions of drought, the presence of small quantities of water in the apoplast may explain the survival of the dehydrated thallus. Antarctica, Lichens, Scanning Electron Microscopy in Back Scattered Mode (SEM-BSE), Low Temperature Scanning Electron Microscopy (LTSEM), Water relations, EPS