Mina Bissell of the Lawrence Berkeley Laboratory in California, USA, has long pointed out that micro-environment plays an important role in the development of cancer. Cancer cells, just like any other cells in the body, exist in their own 'micro-environment' consisting of the rest of the tissue. Now, by creating what she calls 'designer micro-environments' in which she changes the environment of breast cancer cells and the three-dimensional structure of the tissue in which they are embedded, Bissell shows that breast cancer can be made to stop spreading. This is an important insight into what causes cancer, and carries implications for treatment.