There are a range of kits available that vary with their contents and learning processes. Some of the kits come with microscopes that children can use to observe tiny organisms.
You can also find sets that have experiments for children to carry out that include mini volcanic eruptions, crystal growing sets, and digging kits. Some of these sets come with educational booklets that children can read through after doing the experiments to learn more.
Some sets allow girls and boys to learn more about the science behind motors and engineering by making their own mini robots. So, these sets can vary a lot in their contents and what children can learn from them.