Nowadays, an identity card is a staple feature of any purse or wallet and its holder is rarely without it. However, that hasn't always been the case. While laissez-passer documents for crossing borders have been around for centuries, the requirement to hold an official identity document only dates back to the First World War, when European countries introduced passports so that they could identify their own nationals and carry out border checks for security purposes. When the war ended, the requirement to present a passport at borders remained in place.
In 1920, a Conference on Passports, Customs Formalities and Through Tickets was held in Paris under the auspices of the League of Nations. Signatory states standardised the passport's format – adopting a booklet form – and contents. Today, the International Civil Aviation Organization, a UN specialised agency, is responsible for passport standardisation.
Following the 1957 European Agreement on Regulations governing the Movement of Persons between Member States of the Council of Europe, Swiss citizens only needed a valid identity card to travel within Europe. More recently, Switzerland's entry into the Schengen Area in 2004 means that its citizens can cross European borders without even having to show an ID card.
Outside Europe, Switzerland has bilateral agreements exempting nationals of state parties from a visa requirement for stays of up to three months without gainful employment. Such agreements exist with Chile, Hong Kong and Brazil, among others. This means it is now possible to set off around the world with just an identity document in one pocket and a plane ticket in the other – even on the spur of the moment!