How many stickers do you know?

In 1840, the world's first postage stamp was introduced. At that time, these early stamps had no perforations and no adhesive on the back, making them difficult to use. As a solution, later versions were coated with a special gum that activated when wet, allowing users to easily stick them onto letters with just a bit of water. By the 1960s and 1970s, countries like Sierra Leone and Tonga began issuing self-adhesive stamps, also known as "stickers." These stamps could be applied without the need for water, making them more convenient. Today, over 70 countries and regions have adopted this technology. China introduced its own self-adhesive stamps in 2004. On September 30, 2004, China released a special stamp featuring the National Flag Emblem of the Peopleâ€™s Republic of China, along with a small version of a perforated hole (with a print run of 700,000). It also issued a small version of the "Chinese People's Republic National Emblem (Self-Adhesive)" (with a print run of 500,000), marking the official start of China's self-adhesive stamp collection. In 2005, China continued to expand its self-adhesive series. On June 1, the "Hans Christian Andersen Fairy Tales (Adhesive)" mini-sheet was released, with a circulation of 2.65 million. Later that year, on November 12, the "29th Olympic Games - Emblem and Mascot (Adhesive)" mini-sheet was issued, with a print run of 5.5 million. The following years saw several more Olympic-themed self-adhesive stamps. In March 2006, the "Dog (Adhesive)" mini-sheet was released, followed by the "29th Olympic Games - Sports (A) (Stickers)" on August 8, 2006, with a circulation of 2,999,800. The "29th Olympic Games - Sports (B) (Self-Adhesive)" came out on August 8, 2007, with 3 million copies. On December 20, 2007, the "29th Olympic Games - Competition Venue (Self-Adhesive)" mini-sheet was issued, with a print run of 3.5 million. In 2008, China continued its Olympic theme with the "29th Olympic Games - Torch Relay (Adhesive)" mini-sheet (3.5 million copies) and the "Olympic Games from Beijing to London (Stickers)" (1.9 million copies). Additionally, three small bills were released between 2007 and 2009, including "Guo Rongrang Pear (Adhesive)" (5.99 million), "Cao Chong Xiang Xiang (Self-Adhesive)" (6.7975 million), and "Blessings for the Fatherland (Adhesive)" (6,592,200). Overall, self-adhesive stamps can be categorized into two forms: mini-sheets and small-sized stamps. They also cover two main themes: major political and economic events, and cultural or children's topics. From a collectible perspective, while stamps with a circulation above 2 million may not yet show significant appreciation, those with smaller print runsâ€”such as the 500,000-copy "People's Republic of China National Emblem (Resin)" editionâ€”are worth considering for long-term holding. These limited editions are especially valuable and should be acquired promptly.