How many films has Martin Scorsese made with Robert de Niro?

Explanation

Robert De Niro has been in 8 films directed by Martin Scorsese, from 'Mean Streets' in 1973 to 'Casino' in 1995. Later on, Leonardo DiCaprio became a Scorsese favourite, and they have so far made four films together. Rumours are that Scorsese and De Niro might make a 'Taxi Driver 2' in the future.