What is matter? Matter is what we and everything in the universe is made of. Everything around us, from desks to books to our bodies, is made up of atoms so small that millions of them can fit inside a single strand of human hair. Inside each atom is a small nucleus and a cloud of electrons orbiting the nucleus. The nucleus is composed of protons and neutrons, and as you zoom in further, you will notice that there are even smaller particles within each, namely the quarks. Quarks, along with electrons, are nature's smallest particles and the indivisible elementary particles that have existed since the Big Bang, some 14 billion years ago. The 92 different chemical elements, of which all ordinary materials are made, were formed billions of years ago in the Big Bang, within stars and in intense stellar explosions.This very brief introduction takes us on a journey from the human scale of matter to the familiar, everyday forms of solids, liquids and plasma gases, the strange forms of quantum matter and antimatter. On larger scales, matter is transformed by gravity into planets, stars, galaxies, and massive galaxy clusters. However, all the items we commonly encounter constitute only 5 percent of the available material. The remaining 95% exists in two mysterious forms: dark matter anddark energy. Dark matter is essential to keep galaxies from receding, and dark energy is needed to explain the observed acceleration of the expansion of the Universe. Jeff Cattrall reviews the latest research on matter and reveals that we still don't know much about the materials our universe is made of.About the AuthorJeff Cattrall received his PhD in radio astronomy from the Cavendish Laboratory at the University of Cambridge. After researching contact electrification of solidified rare-earth gases at near-zero absolute temperature at UMIST in Manchester, he joined the UKAEA Colham Laboratory and worked on the European Joint Torus Experiment (JET), of which he became the meeting leader.