Throughout human history, the invention and improvement of telescope occupied an indispensable place in the advancement of astronomy. And this blog is devoted to introducing the history of telescope in last four hundred years. The earliest known workingtelescopewas created by Hans Lippersheyin 1608 to “see things far away as if they are nearby”. Restricted by the knowledge and technology in that period, this original telescope had a quite simple structure when comparing with far-advanced large reflecting telescopes nowadays. It consists only of a convex and a concave lens and has only 3 times magnification. Still such kind of telescope spread rapidly after its appearance and opened the gates to the revolution in observational astronomy in later years. Soon after its introduction to Italy, Galileo, one of the most prominent scientist in modern science, improved and perfected the telescope by grinding his own glasses and change the arrangement of lenses. His masterpiece, “Galileo’s telescope”, became the prototype of modern day refracting telescope, with the difference that the objective lens and eye lens of his telescope was made of different lenses, while modern ones made use of two convex lenses. And when we stepped into the 20th century, scientists began to build large research reflectors , such as the 60-inch Hale telescope in 1908 and 100-inch Hooker telescope in 1917 to fulfill their demand for precision photographic imaging that could not be achieved by refracting telescopes before. And with the fast development of science in post-war periods, active and adaptive optics, together with infrared, X-ray and Gamma-ray telescopes , were also employed in discovering unknown parts of our universe that haven’t been touched before.