Our knowledge on cyanobacterial molecular biology increased tremendously by the 
application of the "omics" techniques. Only recently, metabolomics was applied 
systematically to model cyanobacteria. Metabolomics, the quantitative estimation 
of ideally the complete set of cellular metabolites, is particularly well suited 
to mirror cellular metabolism and its flexibility under diverse conditions. 
Traditionally, small sets of metabolites are quantified in targeted metabolome 
approaches. The development of separation technologies coupled to 
mass-spectroscopy- or nuclear-magnetic-resonance-based identification of low 
molecular mass molecules presently allows the profiling of hundreds of 
metabolites of diverse chemical nature. Metabolome analysis was applied to 
characterize changes in the cyanobacterial primary metabolism under diverse 
environmental conditions or in defined mutants. The resulting lists of 
metabolites and their steady state concentrations in combination with 
transcriptomics can be used in system biology approaches. The application of 
stable isotopes in fluxomics, i.e. the quantitative estimation of carbon and 
nitrogen fluxes through the biochemical network, has only rarely been applied to 
cyanobacteria, but particularly this technique will allow the making of kinetic 
models of cyanobacterial systems. The further application of metabolomics in the 
concert of other "omics" technologies will not only broaden our knowledge, but 
will also certainly strengthen the base for the biotechnological application of 
cyanobacteria.