During the maturation phase of flower development, the onset of anthesis visibly marks the transition from buds to open flowers, when petals stretch out, nectar secretion commences and pollination occurs. The analysis of the metabolic changes occurring during this peculiar developmental transition have primarily focused attention on specific classes of metabolites, such as pigments and scent emission and far less on the whole network of primary and secondary metabolites. To investigate the metabolic changes occurring at anthesis, we performed multi-platform metabolomics alongside RNA sequencing in individual florets harvested from the main inflorescence of Arabidopsis thaliana ecotype Col-0. To trace the metabolic fluxes at the level of the whole inflorescence and individual florets, we further integrated these studies with radiolabeled experiments. These extensive analyses revealed high-energy level metabolism and transport of carbohydrates and amino acids supporting intense metabolic rearrangements occurring at the time of this floral transition. These comprehensive data are discussed in the context of our current understanding of the metabolic shifts underlying flower opening.