A new open access article in Scientific Reports details the role of extracellular matrix (ECM) stiffness in regulating breast cancer cell activity by testing cell growth on a variety of 2D and 3D substrates. Researchers found that the highest proliferation rates occurred in the softest 3D hydrogels tested – providing more evidence for the need of 3D culture systems recapitulating the native microenvironment in order to reveal disease-relevant phenotypes. Gels were imaged using a Nikon Eclipse Ni-U upright research microscope.