The location of sponges (Porifera) at the base of the tree of origin of all multicellular organisms on our planet determines constant scientific interest in their study as model organisms. Sponge skeletons are biocomposite-containing 3D structures formed by minerals (silica, calcium carbonates) and organic phases with a clearly defined nanostructural organization. Nanofibrillar fundamental biopolymers such as chitin, spongin, collagens and actin take part in the formation of the unique bioarchitecture of poriferan skeletons. In this chapter, we discuss the current state of the work related to sponges’ bioinspired materials science and biomimetics, taking inspiration from structural biology and unique biomineralogical scenarios discovered in these ancient-in-origin organisms.