The dispersal of that heat sets an overall body temperature, with different types of cells contributing to varying degrees. Because the fluid in cells is water-based, scientists have generally assumed it carries heat much like water does. Instead heat dissipates in cells about five times more slowly—a speed more akin to the way it dissipates in oil. Until now “nobody knew this basic property of living cells,” Suzuki says. The heat conductivity identified in the new work can explain smaller heat spikes of a couple of degrees F, though not the massive heat surge in mitochondria, Suzuki says.