This is a craft I did with my son 3 or so years ago that I've been wanting to do again, so here it is...
1 Bag Uncooked White Rice (dollar store)
Liquid Food Coloring (we used neon)
1. Separate rice between baggies
2. Pour in 2 tablespoons of vinegar per 1 cup of rice and 4 drops of food coloring per 1 cup rice
3. Squeeze out air and seal baggy
4. Pour rice out onto a flat baking pan and store in a safe place (turned off oven) until dry