LMB scientists use mouse models of human diseases in their research where there are no suitable alternatives. The image for day 125 of #LMB365 shows a genetically modified mouse with a black and white patchwork coloured coat. This mouse is known as a chimera and results from the injection of genetically modified embryonic stem (ES) cells derived from a black mouse, into a donor blastocyst from a white wild type mouse. This technique provides LMB researchers with physiologically relevant mouse models of human diseases, including Alzheimer’s, cancer and asthma, with the aim of identifying a new therapy or cure.