Here we describe a spectral imaging system for minimally invasive identification, localization, and relative quantification of pigments in cells and microbial communities. The modularity of the system allows pigment detection on spatial scales ranging from the single-cell level to regions whose areas are several tens of square centimeters. For pigment identification in vivo absorption and/or autofluorescence spectra are used as the analytical signals. Along with the hardware, which is easy to transport and simple to assemble and allows rapid measurement, we describe newly developed software that allows highly sensitive and pigment-specific analyses of the hyperspectral data. We also propose and describe a number of applications of the system for microbial ecology, including identification of pigments in living cells and high-spatial-resolution imaging of pigments and the associated phototrophic groups in complex microbial communities, such as photosynthetic endolithic biofilms, microbial mats, and intertidal sediments. This system provides new possibilities for studying the role of spatial organization of microorganisms in the ecological functioning of complex benthic microbial communities or for noninvasively monitoring changes in the spatial organization and/or composition of a microbial community in response to changing environmental factors.Spectral imaging is a technique in which spectral information (i.e., the spectrum of light that is scattered from, transmitted through, or emitted by an object) is acquired at every location in an image. Since the spectral information reflects the object's identity, status, and/or composition, combining it with spatial information (i.e., the size, shape, and location of the object) enhances our ability to unravel and understand possible links between the spatial organization and functional relationships for constituents of a system. These attributes have made spectral imaging important in various areas of basic research and in industrial applications.Generally, previously described methods concentrated either on very large scales (e.g., astronomy and satellite or airborne remote sensing of the Earth) or on very small scales (e.g., microscopic observations in medicine and microbiology). In the field of benthic microbial ecology, which is the focus of this paper, large-scale spectral imaging techniques generally aim to identify pigments or to quantify biomass concentrations in microbial communities spread over several meters to kilometers, such as intertidal flats (5,6,17,20). Such techniques usually employ airborne imagers to detect reflected light in several tens of spectral bands covering visible and near-infrared regions. The spectral reflectance data are calibrated and validated by combining ground truth measurements of the parameters of interest (e.g., pigment content) with the spectral reflectance measurements obtained using single-point spectrometers, which detect the signals from regions whose areas are several square centimeters to several square decimeters. Quali...