Developments in SEM played a major role in the discovery of new minerals / mineral phases associated with lichens and potential tolerance mechanisms to environmental stress and in elucidating species concepts. (A) First x-ray emission map showing Fe localization in the cortex of Acarospora smaragdula; (B-C) SEM images of Acarospora smaragdula agg. sampled from a concrete fencepost subjected to extreme metal particulate fall-out and sulphur dioxide pollution in Zlatna, Romania (see Figure 3B); (B) Secondary electron field emission scanning electron microscope (FESEM) image of microbotryoidal granules of Pb/S/Sn phases visible down to 20 nm which may be primary in origin (i.e. of smelter origin) or secondarily mobilized within the lichen. (C) X-ray emission map for Pb mainly localized on the surface and medulla. (D) SEM micrographs of crystalline inclusions within the medulla of Acarospora rugulosa (Figure 2D). (E) SEM micrographs of crystals in Cu-rich cortices in Acarospora smaragdula (Alstrup 77899). [Figure 4A adapted from Figure 2, Noeske et al., 1970; Figure 4B adapted from Figure 4C, Purvis et al., 2000; Figure 4C adapted from Figure 2A, Purvis et al., 2000; Figure 4d adapted from Figure 2A, Purvis, 1984; Figure 4E adapted from Figure 4B, Purvis et al., 1987.