I do not even know where to start! I will just come out and say it, this is one of Scorsese's best films and it's really right up there next to GOOD FELLAS. This was a masterpiece of film making! The acting, the characters, the settings, the plot twists, the violence and the story, everything just melted together perfectly. There are so many characters, each with an amazing side story to tell and in the end, it all comes together. DiCaprio plays Billy Costigan, the undercover cop trying to infiltrate the Irish Mob. This kid just keeps getting better and better with each new film. His character's determination to stay undercover is the only reason he can conceal his fear and survive in the barbaric underworld that he is living in. You really get a sense of the fragile emotional state he is experiencing, while on the surface you see him as a ruthless thug. Great stuff!! Matt Damon plays Colin Sullivan, the other cop who is an informant for the mob. Damon definitely brought his “A” game! It's amazing to see the dichotomy between these two main characters and how they deal with the exact same stress but with completely opposite issues. Jack Nicholson plays Irish gang leader Frank Costello. One word…WOW! I really dig seeing Nicholson not being Nicholson, he totally owned this character with his ruthlessness and charismatic demeanor. I can go on about each of the other supporting characters, but there are just too many to talk about and they all bring something to the table.