The LHC experiments involve some of the largest and most complex experimental apparatus ever devised. They rely on large collaborations of physicists and engineers from all over the globe, and their conception, design and construction took years - even decades - to complete. This year three of them celebrate their 20th anniversaries.

In June 1993, ATLAS and CMS, the two general-purpose experiments at the LHC, received the provisional go-ahead to submit technical proposals . It was the start of a difficult but amazing path to last year’s major discovery of a Higgs boson.

The technical proposals were duly submitted in 1995 and approval followed in 1996. The formal approval for construction was given on 1 July 1997 by the then director-general, Chris Llewellyn Smith, based on the recommendations of the Research Board and the LHC Committee.

Two other LHC experiments, ALICE and LHCb, also have their origins around the same time. ALICE submitted a letter of intent to the LHC Committee in March 1993.  LHCb, which has its origins in three separate proposals to investigate B-meson decays, COBEX, LHB and GAJET, submitted their letter of intent some two years later in August 1995.

To mark the 20 years of ALICE the collaboration have released a timeline of the experiment.

For an overview of the conception and construction of the LHC and its experiments see the October 2008 issue of the CERN Courier.