It may have fewer than many of the other sciences, but biology does have two dozen or so “rules”—broad generalizations about the behavior or nature and evolution. Now, USC researchers want to add a new rule called “selectively advantageous instability (SAI),” which explores how instability can actually benefit a cell and a cellular organism. Across the sciences, rules and laws help us make sense of the world around us, whether applied to cosmic scales or subatomic ones. However, in the biological world, things are a bit more complicated. Another “law,” known as Bergmann’s rule, states that species of a broadly distributed clade tend to be larger in colder climates and smaller in warmer ones (though of course, as with most biological rules, exceptions apply ).