What are paper made from?

Main ingredient of all paper is cellulose fiber obtained from plant. Loading or filling material such as clay, CaCO3, Talc, TiO2 etc. are used for higher brightness and better printability. Rosin, alum or combination of other chemicals is used to make paper water resistant. Some special purpose paper such as coffee filter paper contain wet strength polymer so to withstand hot water soaking. Colored paper may contain dye or pigment.