Invertebrates are animals without backbones and there are millions of different sorts on our planet. Many have a hard 'shell' on the outside which gives them their shape. They have a soft inside which includes mussels.
Insects are invertebrates which have a hard 'outside', and a soft inside (that means that they go "scrunch, then squish" when you step on one by mistake - yuk!).
Some invertebrates have a soft inside and a soft outside:
OK, so it's time to find out more about INVERTEBRATES, what they're like and how they are sorted out into groups. Let's get sorting!