The history of condoms goes back at least several centuries, and perhaps beyond. For most of their history, condoms have been used both as a method of birth control, and as a protective measure against sexually transmitted infections such as syphilis, gonorrhea, chlamydia, hepatitis B and more recently HIV/AIDS. Condoms have been made from a variety of materials; prior to the 19th century, chemically treated linen and animal tissue (intestine or bladder) are the best documented varieties. Rubber condoms gained popularity in the mid-19th century, and in the early 20th century major advances were made in manufacturing techniques. Prior to the introduction of the combined oral contraceptive pill, condoms were the most popular birth control method in the Western world. In the second half of the 20th century, the low cost of condoms contributed to their importance in family planning programs throughout the developing world. Condoms have also become increasingly important in efforts to fight the AIDS pandemic.