Organic chemicals sometimes have isomers. This means that they have the same numbers of atoms of the different elements, but they are arranged differently in the structure. In a chiral molecule, the structure of both isomers is exactly the same except that they are mirror images of each other. The word "chiral" comes from the Greek word for hand, because hands are a good example of what it is. When you hold your hands in front of you, you can see that they are exactly the same, structurally, but they cannot be superimposed because they are mirror images. How can you tell if a molecule is chiral? You need to find a carbon atom in the molecule which has four different groups attached to it. The tetrahedral arrangement of these groups around the carbon atom means that there will be a chiral "stereoisomer" of that molecule. To find the stereoisomer you must draw the molecule as a tetrahedron and then draw its mirror image. You will see that the two structures cannot be superimposed, the original molecule is chiral. If there are no carbon atoms in the molecule with four different groups, then it is not chiral.