The prickly pear cactus, an abundant, emblematic and highly versatile plant, is now being made into bricks used to build houses in Mexico's rural state of Michoacan. The eco-friendly bricks are the brainchild of materials engineer Javier Guillen. He created a bio-polymer out of sap harvested from the plant, and used it to bind crushed trash with soil to mold the bricks. The inexpensive sustainable bricks can cut down construction cost, offering better living opportunities for residents in rural areas.