Microcosm, Technology museum in Meyrin, Switzerland.

Microcosm was a science museum in Meyrin dedicated to explaining particle physics research. It featured large detector components in its outdoor garden and used interactive displays to make complex laboratory concepts understandable to visitors.

The project was approved by the CERN Directorate in February 1988, and initial construction was largely completed in 1989 with funding from the Canton of Geneva, the Swiss Confederation, neighbouring France, banks and industrial firms. It opened to the public in 1990. A final version, developed with Spanish design team Indissoluble, opened in January 2016. The museum closed permanently on 18 September 2022 and was replaced by the CERN Science Gateway, inaugurated on 7 October 2023.

The garden, named Léon Van Hove Square after CERN's Research Director-General from 1976 to 1980, displays large components of retired CERN experiments outdoors. Inside, a 1:1 slice model of the CMS detector and a real-time cosmic ray detector showed how experiments are built and run.

Microcosm stood at CERN in the canton of Geneva, near the town of Meyrin on the Swiss-French border. Entrance was free and needed no reservation, and the museum opened six days a week. The large detector and accelerator parts were displayed outside in the adjacent garden, named Léon Van Hove Square.

The annex held the central tracker of the UA1 detector, used at the Super Proton Synchrotron from 1981 to 1984, where the W and Z bosons were discovered. The garden, named Léon Van Hove Square after CERN's Research Director-General from 1976 to 1980, displays large components of retired experiments outdoors.