Living cells are the basic building blocks of all organisms. We, as humans, are essentially a collection of trillions of living cells: and all these cells emerge from a single fertilized egg. This means that “mitosis” (or cell division) is one of the most fundamental and important processes of life. It is known that cells change drastically in shape and mechanical properties when they divide. For instance, the protein layer beneath the outer membrane stiffens and ‘rounds up’ becoming more spherical. However, up to now, little was known about what goes on inside the cell during mitosis. In this study, researchers led by MBExC member Timo Betz used optical tweezers to reveal that inside the cell it softens and fluidifies (becomes more fluid), while also becoming less active during cell division. The results of this study were published in Nature Physics.