Mass spectrometry （MS） has been used to quantify endogenous levels of plant metabolites. However, standard analyses, for example, with gas-chromatography MS or liquid-chromatography MS require a relatively large amount of plant materials. Therefore, it has been difficult to know exactly the levels of target molecules at specific tissues or cells by the methods. On the other hand, imaging MS and single-cell MS are potentially suitable techniques for visualizing local distribution of various chemical compounds in plants at tissue and single cell levels, although they are not yet commonly used in plant science studies. The four feature articles in this volume describe the current status of research using imaging MS and single-cell MS.
