2001太空漫遊.

the meaning to the ending is intended for the audience to decide -- open ending. When Dave leaves the base, he is supposed to be travelling through a time-warp (or you can call it Black Hole), when he stops, he sees an old man in a room... that old man is played by the same actor as Dave. He then looks again, and he sees himself in bed, aging and finally turning into an embryo-type being, The black tablet/stone could be interpreted as a door-way through time, or some even think of it as the gateway to Heaven -- the director and writer didn't want to give the movie a definite ending, but they did want the audience to think more about the connection between space, mankind, religion, and science.

I could be confusing you even more by writing the above, but it's a great movie that allows you to keep thinking about it -- with age, you will also have even more opinions and interpretations from each viewing.