Figure 1 shows the photographs of nanoporous cellulose films prepared from 7 wt% cellulose solution. As seen, the nanoporous cellulose film appears translucent which is indicative of the porous material. In this case, nanoporous structure was achieved by treatment of cellulose hydrogel film using multiple freeze/thaw cycles. To maintain the pore structure, nanoporous cellulose hydrogel was treated in a solution of 30 wt% glycerol. In contrast, cellulose film without glycerol aftertreatment shrinks drastically due to the collapse of the pore skeleton. It is reasonable to say that glycerol is absorbed into cellulose skeleton and then acts as a plasticizer to maintain the dimensional stability of the nanoporous structure. When observed by SEM, pore size and pore distribution are revealed. A variety of pore sizes were controlled by time of freezing, a number of freeze/thaw cycles and cellulose concentration. In the absence of glycerol aftertreatment (Figure 2A), cellulose film exhibits continuous surface without any pore.