Breast cancer metastatic culture. Fluorescence light micrograph of organoid stem cell cultures of mammary (breast) tissue. Organoids are miniature versions of organs grown in the laboratory to allow testing of targeted therapies. This technique also helps identify networks of genes that control cellular behaviours and lead to cancers. This organoid was grown from a single mammary stem cell. It was used to demonstrate the criticality of the Sox10 gene (blue). When Sox10 is highly expressed in cells, they turn off cytokeratin expression (red and green) and attempt to migrate out of the organoid (right). These disseminated cells then have the capacity to form new organoids (or new secondary or metastatic cancers).