Fold a paper towel and spray it with water. Put a paper towel and three lima beans (that had been soaked in water for about an hour) into a Ziploc bag. The Ziploc bags should be stapled inside the greenhouses and attached to a bulletin board where the class can watch the seeds grow.
Colour exploration. Includes kaleidescopes, holographic spinners, mirrors and coloured perspex circles. The coloured circles also lead to lots of colour mixing conversations about what happens when you put two different coloured circles on top of each other and then look through them!