Severus Snape looks in the pensieve where he has stored some memories from his life, in particular from his unhappy childhood and his youth, memories mainly of the two women that were important to him: his mother, Eileen Prince (married to Tobias Snape, Severus abusive father), and his school-friend Lily Evans, who later became Lily Potter, Harry's mother.
Actors:
Teenage Snape: Diego Luna (from Soldados de Salamina)
Lily Evans: Kirsten Dunst (from Spiderman 2)
Music: All I Need by Within Temptation
Lyrics:
I'm dying to catch my breath
Oh why don't I ever learn?
I've lost all my trust
Though I've surely tried to trun it around
Can you still see the heart of me?
All my agonies fade away
When you hold me in your embrace
Don't tear me down for all I need
Make my heart a better place
Give me something I can believe
Don't tear me down
You've opened the door now, don't let it close
I'm here on the edge again
I wish I could let it go
I know that I'm only one step away
From turning around
Can you still see. etc
Don't tear me down for all I need
Make my heart a better place
Give me something I can believe
Don't tear it down, what's left of me
Make my heart a better place
I tried many times but nothing was real
Make it fade away, don't break me down
I want to believe that this is for real
Save me from my fear
Don't tear my down. etc