Get 1 rectangle backing dish with lid. Preheat oven to 400 degrees F. Shred both cheeses and mix together.
Spread a thin layer of refried beans across the bottom of dish. Spoon a thin layer of salsa over the beans. Spread a thin layer of sour cream over salsa. Spread a thin layer of shredded cheese over salsa. (Repeat process till you have used all your beans, cheese and salsa)
Bake in oven for 10 minutes, till cheese is melted. Let stand for 5 minutes before serving. Serve with tortilla chips.