Inception had my mind struggling to understand the dream in a dream in a dream and how they wake up with a kick and not to forget 5 minutes sleep equals one hour in dream world. Meanwhile while we learn about Cobb and Mal, that they have been living in a dream world an grew old together how did they do that? Their bodies had to be fed and kept alive. In Mombasa when Cobb goes looking for the Chemist we see how people live in the dream world only but they mention they come there for 3 to 4 hours a day, they are not 24/7 hooked up.
The movies starts with Cobb washing ashore and being taken by guards to an old man, later on we learn that it happens in the dream world or more specifically, in Limbo. This infographic clearly shows each dream, whose dream they are and the kicks. During the movie we learn about the totems and why they have one. In the end we see Cobb spin the spinner and it keeps spinning. We know that Cobb is the only one who knows how long the spinner will spin and that in a dream he can make it spin endlessly. So we are left to doubt if he really got back to his kids in real life or if the whole thing was actually a dream from which he never woke up.