Ive De Smet leads the Functional Phosphoproteomics Group. To fully understand plant growth and development, we need to identify novel components and require insight in the underlying network. In this context, there is an urgent need to gain insight in protein changes on different levels, including protein-protein interactions and post-translational protein modifications. With respect to the latter, temporary and reversible phosphorylation of proteins is essential in regulating intracellular biological processes. Phosphorylation affects protein folding (conformation), protein function and the regulation of enzymatic activities, defines substrate specificity, and influences protein localization, complex formation and degradation. The mechanistic importance of phosphorylation is obvious from its major influence on various cell functions, such as signal transduction, cell division, cell differentiation, and metabolic maintenance.