In the limelight
At the centre of attention.
Limelight really was made using lime.
Limelight is an intense white light which is produced by heating a piece of lime in a flame of burning oxygen and hydrogen. The effect was discovered in the 1820s by Goldsworthy Gurney and the application of the process to create a bright light was developed by Thomas Drummond around 1825. It was widely used in 19th century theatres to illuminate the stage and was first used in a public theatre at Covent Garden in London in 1837.
Clearly, actors who were the centre of attention on stage being said to be in the limelight. The figurative use, to people or things that were the centre of attention outside the world of theatre, came into use around the turn of the 20th century; for example, this piece from The New York Times, July 1902:
"William S. Devery was in the limelight last evening. Tens of thousands of people of the district crowded the streets in the neighborhood and shouted the name of the ex-Chief of Police of New York."