Our first science unit for 3rd grade was a unit on Kidneys. I usually ask Wally what he wants to learn about for Science, and he usually chooses constellations and robots. Every time I ask. Same thing. This year, he added geology. And I added kidneys.
We made an artificial kidney (or so said the kit I bought – I would call it mini dialysis machine) and we dissected a real kidney. It was fun. There were pictures of people peeing. Bonus learning: do not eat or drink science chemicals.
If you want to read more, here’s the link: http://thefamilyschool.wordpress.com/2012/09/03/kidney-unit/