Sherlock Holmes made his debut in 1887, a detective novel, A Study of Blood Characters. However, at that time, the novel did not cause much sensation. Sherlock Holmes really became famous in 1890, another novel, Four Signs. The magnifying glass is the first prop of Sherlock Holmes' standard equipment, which made its debut in a study on the role of blood. Holmes used it to survey the word "Rachel" on the wall, and the magnifying glass became synonymous with many detectives in the future. Even real detectives will use it to mark their detective status. For example, Dr. Li Changyu often carries a magnifying glass with him to analyze the blood at the crime scene. Sherlock Holmes is famous for Conan Doyle, but Conan Doyle is famous for Sherlock Holmes.