Symmetry is one of those math concepts that I enjoy teaching.
The main reason I love teaching about symmetry is because there are so many fun ways to do it!
Glow in the Dark Blob Aliens are at the top of my list of fun ways to teach symmetry!
Buy a bottle of florescent paint. Have your preschoolers use a dropper to drop several large drops of the florescent paint into the middle of a piece of black construction paper. Fold it in half (long way). Have your preschooler smash and rub the paint around inside the folded paper. When you open it you will have an awesome looking blob. Give your preschooler googly eyes to add to their alien.
When your aliens are dry, hang them on your bulletin board. They are going to look amazing on your glow in the dark day!