Abstract: In the ΛCDM paradigm, 95% of the Universe consists of dark energy and cold dark matter, but the low-density cores of dark matter measured at the centre of galaxies are hard to explain using this model; here a review of recent work shows that the action of stars and gas can significantly alter the distribution of cold dark matter through a coupling based on rapid gravitational potential fluctuations. The ΛCDM or Lambda-CDM model has been regarded as the standard model of cosmology for decade or so, as it explains many of the most important observations. The model assumes that the 95% of mass and energy of the Universe not accounted for in the visible Universe is present as dark energy (Λ) and cold dark matter (CDM). Where it does fall down, though, is in its apparent inability to explain the low-density 'cores' of dark matter measured at the centres of galaxies. Historically, the effects of normal matter on the dark matter have been ignored. In this review, Andrew Pontzen and Fabio Governato point to recent work that shows how gas and stars can significantly alter the effect of CDM through a coupling based on rapid gravitational potential fluctuations. A principal discovery in modern cosmology is that standard model particles comprise only 5 per cent of the mass-energy budget of the Universe. In the ΛCDM paradigm, the remaining 95 per cent consists of dark energy (Λ) and cold dark matter. ΛCDM is being challenged by its apparent inability to explain the low-density 'cores' of dark matter measured at the centre of galaxies, where centrally concentrated high-density 'cusps' were predicted. But before drawing conclusions, it is necessary to include the effect of gas and stars, historically seen as passive components of galaxies. We now understand that these can inject heat energy into the cold dark matter through a coupling based on rapid gravitational potential fluctuations, explaining the observed low central densities.