Heterogeneity constitutes a critical barrier to treating cancer. This Review discusses the biological and physical sources of heterogeneity across length scales, encompassing tumour-cell-intrinsic, tissue-microenvironment and organism-level sources, and how engineering strategies can improve our understanding of these phenomena.

Obesity worsens cancer-specific survival and all-cause mortality for women diagnosed with breast cancer. Rich in adipose tissue, the breast exhibits increased adipocyte size in obesity, which correlat...