Why do Catholics put Ashes on our heads on Ash Wednesday?

Ìâ‰âÂÌâÅÒExcuse me, you've got some dirt on your head.' Every year someone says that to me on Ash Wednesday. Maybe it has happened to you too. In the past it used to frustrate me, but in recent years I have come to see it as a great opportunity to evangelize, to share with someone about the most important person in my life: Jesus Christ.