We have developed an open-source Internet Emulator, which is a Python library, consisting of the classes for each essential element of the Internet, including autonomous system, network, host, router, BGP router, Internet exchange, etc. It also includes classes for a variety of services, including Web, DHCP, DNS, Botnet, Darknet, and Blockchain. Many other interesting network technologies can also be deployed on the emulator. Using this library, users can easily construct a miniature Internet. Although it is small, it has all the essential elements of the real Internet. The construction is compiled into Docker container files, and the emulation is executed by Docker on a single machine, or on multiple cloud machines. This emulator has been primarily used for education since it was released in August 2021, but recently several research groups have started to use it for their research. In this paper, we present the design of this emulator and its applications. This work is still in its early stage, so the objective of this paper is to get feedback from the community, so it can be more useful to research and education.