The Beatles cast such a large shadow over their contemporaries -- even the most popular of them -- that sometimes it's difficult to distinguish what they actually contributed to the world of pop music and what they simply popularized. Something they definitely did do was open the floodgates for the British Invasion of the '60s, beginning, for all intents and purposes, with Ed Sullivan's portentous introduction in the beginning of 1964: "Ladies and gentlemen, the Beatles." Popular music has never been the same; at least that's definite. They were also one of the first bands to take rock 'n' roll and merge it with other forms like popular standards, folk (with a little help from Bob Dylan), blues, etc. And although they are often derided for their weaknesses as a true-blue, hard-living, hard-rocking, parent-frightening, cooler-than-all band, one need only compare the versions of "I Wanna Be Your Man" as done by the Fab Four and by the Rolling Stones; their early days in Hamburg taught them well the rules of blistering rock 'n' roll. At least their retreat from the stage was matched by a wealth of awesome material -- everything from the "Penny Lane" / "Strawberry Fields Forever" single to what was to be the band's death knell, "The End" off of Abbey Road, was arguably the most advanced popular music of the time. They had the resources, the talent, the producer ("fifth Beatle" George Martin) and the desire to push the boundaries of their music. Even more amazing is that it has maintained such a grip on the public's ear and imagination.