This introduction will cover the 20 years which brought the LHC experiments from vague conceptual ideas to what can be seen at CERN in the various experimental halls today. The topics covered will go chronologically from the conceptual design and initial assessment of the physics reach, to the R&D issues tackled and solved between 1990 and 2000, to the construction period with its own challenges of a different nature from those of the R&D phase, and finally to the current integration, installation and commissioning phase and to the preparation for initial operation, data-taking and physics analysis.
No prerequisite knowledge required.