The sole piece of new music on Britneys second greatest hits album, 3 is a simple pop song about, what else, threesomes. But what it lacks in nuance it makes up for in undeniable catchiness representing one of the most successful outings produced yet by Spears and her longtime collaborator Max Martin. It debuted at number one, becoming Spears 3rd song to do so, and also setting a record for the shortest song title to top the chart. No record is too niche for Britney.