A few days ago, the online exhibition "Double School Record: Viewing Harvard and Tsinghua through a microscope" was officially opened. The exhibition was jointly organized by the Department of Science History of Tsinghua University, the Science Museum of Tsinghua University, the Department of Science History of Harvard University, and the Harvard Historical and Scientific Instrument Collection. It is one of the online series exhibitions jointly organized by the Science Museum of Tsinghua University and famous foreign university museums. The microscope is the symbol of modern science. In 1665, when the Great Plague broke out in London, Hooker published the book "Microscopic atlas". The microscope he used can magnify the specimen more than 30 times. After that, Leeuwenhoek of the Netherlands developed a unique single-mode microscope that can magnify more than 200 times. After the 18th century, the microscope gradually circulated around the world, satisfying people's curiosity, revealing the hidden mysteries of nature, and greatly promoting the progress of modern science. Microscopes have also entered university classrooms, laboratories and museums. The online exhibition shows many types of microscopes used, manufactured and collected by Harvard University and Tsinghua University, reflecting the development track of the two world-famous universities in science education, scientific research and historical collection from one side. Two generations of Harvard people's microscopes This exhibition displays a set of Wilson spiral cylinder and compass single-type microscopes produced around 1720. The original purpose of developing such instruments is to meet the growing demand for small portable instruments. This set of microscope originally belonged to Edward Holliot, the ninth president of Harvard University. During his tenure, he strengthened the academic courses in mathematics and science at Harvard University (then Harvard College), and carried out a series of academic reforms, taking academic achievements as the admission criteria of Harvard University. In addition, he also established the first physics laboratory in North America. Harvard University has flourished during his 32-year tenure. Around 1730, the British scientific instrument manufacturer and craftsman Edmund Carpper designed and manufactured a microscope mounted on a triangular bracket. This microscope soon became the most popular compound microscope in the first half of the 18th century, and has been produced for about 100 years. In addition, the exhibition also displays a Kalpeper type microscope, which was produced in the 1850s and is owned and used by Edward Augusto Holliot. He was the son of Edward Holliot. He graduated from Harvard University in 1746. Later, he devoted himself to medical treatment and became a pioneer in the treatment of smallpox in the United States. He vaccinated hundreds of people against smallpox. Holiot lived for 100 years, and in his long and brilliant career, he has seen doctors for 250000 times. He is also a founding member of the Massachusetts Medical Association and the American Academy of Arts and Sciences, and has served as the president of the American Academy of Arts and Sciences. The exhibition of Mark Twain and Children Studying in the United States also exhibited a monocular compound microscope of Mark Twain, a famous American writer. Mark Twain was born in Florida, Missouri, USA in 1835. His original name was Samuel Lanhorn Clemens. Mark Twain literally means twelve feet deep, which is the lowest depth for safe navigation on the Mississippi River at that time. Mark Twain is famous for his travel narrative novels