Filter paper. Coloured scanning electron micrograph (SEM) of the cut end of a piece of filter paper showing its many cellulose fibres. Cellulose is a polysaccharide that is the main constituent of all plant tissues and fibres. Filter paper is a porous material used for separating the liquid and solid parts of a suspension and, being made from wood pulp, is almost pure cellulose. Magnification: x180 when printed 10 centimetres wide.