In this work, we have developed a selective-plane illumination multispectral optoacoustic tomography (MSOT) technique for high-resolution whole-body visualization of intact optically diffusive organisms whose sizes may vary from sub-millimeter up to a centimeter range and beyond. By combining multi-wavelength illumination, the method is shown capable of resolving tissue-specific expression of fluorescent proteins and other molecular biomarkers located deep in living optically diffuse tissues.