They discovered critical time windows in development when compared to the real mouse brain. From stem cells to a correctly-sized brain“In our lab we study how the brain develops from stem cells,” Hippenmeyer explains. They used this novel line to develop a robust and reproducible mouse cortical organoid protocol. To understand how close a developing organoid is to the real brain, it makes sense to look at both in the same species—not to compare a mouse brain with a human organoid, but to study both in the mouse model. In other words, brain stem cells in the organoid lack a proper sense of time.