"bone cells are like small factories making the hard substance of the bone. Also, the fact that you have billions of bone cells in your body and where."
The linked file has a study guide for teaching cell stuff.
METAMIA is a free database of analogy and metaphor. Anyone can contribute or search. The subject matter can be anything. Science is popular, but poetry is encouraged. The goal is to integrate our fluid muses with the stark literalism of a relational database. Metamia is like a girdle for your muses, a cognitive girdle.