Complex sentence: The history of organized fan groups of S.S. Lazio, known in Italian as the "Tifoseria Laziale", began in the late 1960s when small groups of supporters filled the steps of Stadio Olimpico in Rome.
Split into simpler sentences: The history of organized fan groups of S.S. Lazio, known in Italian as the "Tifoseria Laziale". It began in the late 1960s when small groups of supporters filled the steps of Stadio Olimpico in Rome.