What are the mysterious dark matter and dark energy that seem to account for so much of our Universe? Why is the Universe expanding? For the past 30 years, most cosmologists have looked to the ‘standard model’ to answer these questions, and have had wide-ranging success in simulating formation in the universe and matching observational data. But not everything quite fits the predictions. Are these discrepancies down to the interpretation of observations, or is a more fundamental rethink required?