One thing that all insects have in common is that they all have three body regions. They all also have jointed legs.
Insects all contain a head, a thorax and an abdomen. These may vary in size and color, but they can be found in nearly every insect on the planet. Each segment of the body has a cuticle in place which helps the body bend and move. The cuticle stays the same size until the insect sheds and regrows it. All insects also have a breathing system which contains a tube. This tube allows them to take in and expel air.