Breast and ovarian cancers are complex and heterogeneous, and share several features, including genetic predisposition caused by BRCA1/2 mutations. Ovarian cancer is however associated with poor survival relative to breast cancer. Utilizing comprehensive biobanks, high-throughput omics methods and in vitro model systems we aim to advance our understanding of tumour evolution, disease heterogeneity and therapy response, thereby improving our knowledge of the origin and genomic events leading to the development of breast/ovarian cancer. Deeper understanding of key processes involved in tumour initiation, development and maintenance may be translated to precision treatment. Identification of novel therapeutic targets, stratified by histological as well as molecular phenotypes, should transform survival prospects. Improved knowledge of the spatiotemporal molecular landscapes of these malignancies may lead to the development of biologically informed treatment strategies and clinical trials.