Sponges are one kind of the simplest multi-cellular organisms that live in both fresh-water and marine environment. Among the three classes of sponges, two of which produce silicified spicules as their body support. In recent years, peculiar micro-structure and high fiber-performance are found in sponge spicules. While the growth mechanisms of sponge spicules that live in ambient temperature and pressure was thought to be a new bionic way to produce optical-fiber. Therefore, these new discoveries have drawn increasing efforts worldwide to study the biology and biomineralization of sponge spicules and their bionic applications. Through studying the structure, the characteristic, the growth mechanism and mediation in sponge spicules, scientists are learning a new biotechnological route to produce electronic and optical nano-materials in an environmentally benign way. In this contribution, we review the major findings in the study of the micro-structure and optical performances in sponge spicules, and then discuss the progress and significance of studying sponge spicules.