One of the simplest 4-D objects is an analog of the 3-D cube, known as a hypercube or tesseract. Such objects should have eight cubes as “sides” — just as a 3-D cube has six squares as sides, or a 2-D square has four lines as sides. Because our senses are hard-wired for 3-D at best, there’s no way to show a hypercube the way it truly is. But Segerman plays with 3-D projections of the hypercube — and even better, sculptures that show the projections of monkeys hooked up in a hypercube shape.