Don't expect anything too explicit here, even though it's a Playboy production. This documentary is as teasing as the actresses depicted, as they saunter and shimmy in skirts and bikinis but never bare it all, which is OK, since it lets a wider audience take in this comprehensive examination of sex in cinema. Director Kevin Burns is no Ken Burns, but he does get his points across, using footage harkening back to the earliest crude projections -- directors wasted no time in getting scantily clad women to dance in front of hand-cranked cameras -- to pristine images of today's hottest stars. Along the way, notable sex-in-cinema movers and shakers, including Hugh Hefner himself, help explain what obstacles had to be overcome in order for sex to be realistically portrayed on screen. There's an unrated version that's three minutes longer than the R-rated one, so perhaps there's something more, um, penetrating in that one.