Protein, rubber, man-made fiber, and plastics are all polymer compounds. A polymer is a "macromolecule" with a high molecular weight, meaning it is made up of many molecules bonded to each other. The way they are connected to each other determines what a given material is, and what attributes it has. A device called a Fourier Transform Infrared Spectrometer examines molecular structure, or the ways in which molecules are connected to each other.

When a polymer is exposed to infrared radiation, it emits electromagnetic waves (light) with a unique wavelength, depending on its constituent molecules. By carrying out a computerized processing called a Fourier transformation, we can observe each molecule's spectrum (a graph of wavelength and intensity). Each spectrum is unique to a particular molecular structure. We can specify what a material is by finding the matching spectrum from the spectrum library, which includes the spectra of several hundred thousand polymers. A spectrum is just like a person's fingerprint, and the spectrum library is like a fingerprint database at the police department. We will learn interesting facts if we analyze various materials this way. The popular food "nata de coco" and tissue paper belong to the same category, for example, since they both are made of a plant fiber called cellulose.