Cuisenaire rods were invented by Emile Cuisenaire in the early 20th century and popularized by Caleb Gattegno in the 1950s. The rods are integer-length blocks used to teach mathematical concepts like addition, subtraction, multiplication and division visually. The document provides examples of how to use the colored rods to represent and solve math problems involving these operations. It also covers fractions, area, perimeter and symmetry.