Can anyone suggest some simple pre-school science projects i can do with my three to six year olds?

if they tie in with the national curriculum. any key stage 1 teachers out there? what are you doing with your pupils this term? any nice books you can recommend relating to this subject plz?
Answer
Wormeries. with various coloured soil and sand to let them watch the changes as the worms move around. it needs to be narrow and preferably in clear plastic.growing mustard and cress on kitchen towels. can see the development of plant and it can be eaten .disolving food stuffs in water - test for how easy etc. salt, sugar and some non soluble things .