We present a detailed experimental/theoretical study on understanding the fundamental nature of individual cotton fibers from light scattering experiments. For this purpose, we built a new precision nephelometer and calibrated it with quartz fibers. The results were compared against the theoretical predictions based on a finite element model. We showed that scattered intensity profiles Is(θ) can be related the quality (fineness) of cotton. At small scattering angles (θ < 10°), Is(θ) reveal information about the shape (cross section) of cotton fibers. On the other hand, Is(θ) profiles within the range of 30°< θ <50° may be used to evaluate single fiber cotton quality (fineness). In the experiments, iris opening (viewing angle) and scanning range and rate were determined to be the key parameters for precise measurements.