This was really cool to read, for example how the bacteria creates calcite to repair the cracks. It was hard to pick what kind of bacteria to use because most options would die from moisture. First the crack hits a certain point to were it "initiates" the bacteria. Then the bacteria then produces calcite to repair the crack. Finally the crack is slowly repaired and it would also be to expensive for widespread.

I LOVED this book. For a grade 4 it was pretty lengthy but I liked it because there were some pretty cool robots like Tin Man and also liked the argument of which school should get Donovan.