Ultralight materials are a kind of novel materials whose densities are less than 10 mg/cm³. These materials exhibit excellent physical properties, chemical properties and mechanical properties derived from both constituent and structure, which possess high specific strength and specific stiffness. With the excellent properties of ultralight materials, great effort has been devoted to studying ultralight materials. The components of the existed ultralight materials mainly include silica, metal and oxidizing materials, ceramic, polymers, carbon and compounds. Ultralight materials play an important role in the field of aerospace, due to their unique properties such as acoustic absorption, energy absorption, shock absorption and thermal insulation. The effective properties of ultralight materials are defined both by their cellular architecture and the properties of the solid, such as the spatial configuration of voids and solids, the stiffness and strength of solids. They all have significant influence on the properties of materials. In this review, ultralight materials are classified into three types by different structures: aerogel, foam and microlattice. Also, the fabrication methods and constituent of the ultralight materials created in recent work are summarized. In addition, The research prospects and directions of ultralight materials in the future are also briefly discussed by comparison of all kinds of materials.

Contents
1 Introduction
2 Aerogel
2.1 Silica aerogel
2.2 Carbon aerogel
3 Foam
3.1 Metal foam
3.2 Carbon foam
3.3 Polymer foam
4 Microlattice
4.1 Metal microlattice
4.2 Carbon microlattice
4.3 Ceramic microlattie
5 Conclusion