Book excerpt: Celebrate cats in all their flowing, furry glory in Cats Are a Liquid, a charming picture book that examines the unusual physical properties of felines by writer Rebecca Donnelly and illustrator Misa Saburi. Cats fill./ Cats spill./ Cats flow downhill.// Cats tip./ Cats drip./ Cats grip, snip, rip.// Cats are a liquid/ Except when they’re not. Inspired by an Ig Nobel Prize–winning investigation of how cats behave like liquids, this book introduces some of the physical properties of liquids—they adapt to fit a container, they flow like fluids—and is just pure fun. Like its inspiration, it makes you laugh, then think. Back matter includes a brief introduction to the different physical states: solid, liquid, gas.