Magnifying glass with height-adjustable matt black stand By definition, a magnifying glass is a lens that causes light to converge at a single point. Magnifying glasses have always been mysterious objects and it is not known when they were first used: the Archaeological Museum of Heraklion in Greece displays, amongst artefacts from the 15th century BC, several highly polished round ‘stones’ made of transparent glass. Distant relatives of our modern lenses.