Bill Nye is going through a phase - a phase of matter. Check out the ""Phases of Matter"" episode to find out about rock-solid solids, liquidy liquids, and gassy gases. It's phase-tastic! Everything around us is made of stuff called matter, and all matter is made of atoms. Matter is anything that comes in three varieties, what scientists call phases. There are solids like rocks, cookies, and desks. There are liquids like water, honey, and juice. And there are gases, we breathe air and the helium in balloons. The main difference between the three phases is how fast the matter's atoms move. All atoms move around because they have energy. The more energy that's in something, the faster the atoms move. Atoms in an ice cube don't move very much - they're frozen in place. The atoms in liquid water slip and slide around - that's why you can pour it and spill it. Water vapor atoms are moving pretty fast - that's why they float around in air (a mixture of other gasses). Changing