From its emergence out of organic chemistry and physiology a century ago, the history of biochemistry is one of shifting research agendas. For organic chemists, the questions were those of structure and composition, while for physiologists, they were questions of function. The dynamic biochemistry of the mid-20th century centred on catalysis, energy flow and metabolism. The emergence of molecular biology ('practising biochemistry without a licence') introduced information in place of energy as an organizing cellular principle, but in doing so forgot dynamics. For Crick's Central Dogma, information -- signals -- flowed in one direction only. Now, proteomics is enabling molecular biologists to rediscover biochemistry once more. Signalling -- the processes of communication across space and time -- occurs at all biological levels. I will review them, and their potential future. Will the metaphor of signalling provide a new organizing principle, one that recognizes the essentially interactive nature of information flow within metabolic webs?: I discuss first, the conservation of signalling molecules at the cellular level over evolutionary time; secondly, the supracellular level of physiological signalling in multicellular organisms -- hormones and neurons; thirdly, supraorganismic signalling and communication -- from pheromones to speech; and finally, signalling and reception within and outside the biochemical community - how do we/can we communicate with one another and the rest of the world?