Recent research has established redox-dependent thiol modification of proteins as a major regulatory layer superimposed on most cell functional categories in plants. Modern proteomics and forward as well as reverse genetics approaches have enabled the identification of a high number of novel targets of redox regulation. Redox-controlled processes range from metabolism to transport, transcription and translation. Gene activity regulation by transcription factors such as TGA, Athb-9 and RAP2 directly or indirectly is controlled by the redox state. Knowledge on putative redox sensors such as the peroxiredoxins, on redox transmitters including thioredoxins and glutaredoxins and biochemical mechanisms of their linkage to the metabolic redox environment has emerged as the framework of a functional redox regulatory network. Its basic principle is similar in eukaryotic cells and particularly complex in the photosynthesizing chloroplast. Methods and knowledge are now at hand to develop a quantitative understanding of redox signalling and the redox regulatory network in the eukaryotic cell.