Take a peek at the underside of a sea star and you'll be mesmerized by the details. Each of its arms contains a row of squishy tube feet, which help the animal with a variety of functions. Tube feet enable a sea star to glide over the seafloor or attach itself to surfaces. They're also used for feeding—they help pass along food to the animal's oral mouth at the center of its body.
Meanwhile, the top of a sea star might appear to be quite stiff, but it can actually bend and twist into all sorts of shapes. It can do this thanks to an internal skeleton, or endoskeleton, made up of a meshwork of hard plates called ossicles embedded in the animal's tissues. These plates act like armor and protect the sea star's vital organs.