In 1892, Russian scholar Ivanovsky first discovered that the infectious agent of tobacco mosaic disease can pass through a bacterial filter. The filtrate obtained after the diseased leaf juice passes through the filter can infect healthy tobacco leaves again, causing it to become infected. Mosaic disease occurs. In 1898, Dutch biologist Bejelink further confirmed Ivanovsky's results and confirmed that the pathogenic factor could be precipitated from the suspension by ethanol without losing its infectivity, but it could not be grown on artificial culture media. grow. So he believed that the pathogen was an "infectious, living fluid" smaller than bacteria, and named the pathogen: virus. In 1935, American biologist Stanley extracted virus crystals from tobacco mosaic diseased leaves. The virus crystals were pathogenic, indicating that substances generally considered to be life can be processed like simple protein molecules. This incident became a milestone in the development of molecular biology. He also won the Nobel Prize for this work. As research progresses, it has been proven that tobacco mosaic virus crystals contain both nucleic acid and protein components, and only nucleic acid has the ability to infect and replicate. These discoveries not only laid the foundation for virology research, but also made significant contributions to the development of molecular biology