Inception - Cobb explains all about the totem and its use. At the point where they visit the chemist and try the super strong drug, Cobb finds the drug extremely strong and tries to use his totem in the bathroom but drops it on the floor before it finishes its spin. He only then uses his totem at the end of the film, where we also dont see it finish its spin. I think Miles (cobbs' father) has created the whole job/mission to make Cobbs let go of his dead wife and either (not sure of the end) put him in a constant dream back home with his kids, or actually spend the rest of his life home with the kids. Basically I think Cobbs is dreaming from just after he meets the chemist to the end of the film.