Interest in Gangs

I have never had a real interest in Gangs, until this summer. I read a book, Perfect Chemistry, and it really opened my eyes. It is a drama/romantic book, and the main guy character, Alex, is part of a gang called the Latino Blood. Alex has to wear a red and white bandanna, has tattoos, and has to be loyal to the Latino Blood. I was so intrigued by this book that I had to take the opportunity to research more about gangs. I am really interested in how people come about in joining into these gangs, and why they do.