Mathematicians called topologists study the shapes of various objects to characterize and understand them. Dr. Lisa Piccirillo is a topologist who sometimes studies shapes called knots. Shapes that topologists study can exist in different numbers of dimensions: for example, a circle on a piece of paper lives in two dimensional space, but a loop of thread lives in three dimensional space.
Try this activity from Science World to learn more about how shapes behave in different numbers of dimensions. You can also find a video demonstration of this activity from the Institute of Physics.