Aerogels are highly porous, ultra-light (density around 0.1 g/cm3) nanostructured materials. One of their most extraordinary properties is thermal super-insulation, i.e. thermal conductivity below that of air: 0.015 vs 0.025 W/(m.K) in ambient conditions. However, classical silica aerogels are extremely fragile and organic/synthetic (resorcinol-formaldehyde) aerogels may include toxic components, which hinders their wide application. Bio-aerogels are a new generation of aerogels made from biomass-based polymers, mainly polysaccharides. We prepared aerogels from cellulose (“Aerocellulose” /1, 2, 3/) and pectin (“Aeropectin” /4/) via polymer dissolution, coagulation and drying with super-critical CO2. Their density varies from 0.05 to 0.2 g/cm3 and specific surface area is around 200-300 m2/g. Bio-aerogels are mechanically strong materials, with Young’s moduli from 1 to 30 MPa and plastic deformation without breakage up to 60-70% strain. The thermal conductivity of Aeropectin is around 0.015 – 0.020 W/(m.K) making it the first thermal super-insulating fully biomass-based aerogel reported. The thermal conductivity of Aerocellulose is rather “high”, around 0.030-0.035 W/(m.K), due to the presence of large macropores. We demonstrate that by using cellulose functionalization and making polymer-silica interpenetrated aerogel networks the specific surface area increases to 800-900 m2/g and thermal conductivity decreases below that of the air. Bio-aerogels open up many new applications of polysaccharides: in engineering (as thermal superinsulators), medical and pharmaceutical (as scaffolds, matrices for drug controlled release) and electro-chemical when pyrolysed (batteries, fuel cells).