I took this picture from forum aboutcircuits to illustrate current flow in NPN transistor. Here is what I am confused: A few at Figure above(a) fall into holes in the base that contributes to base current flow to the (+) battery terminal. Why these electrons that fall into holes necessary flow into base terminal and contribute to base current flow? Is it possible that there are some electrons fallen into holes and then go straight into collector? Or in other words: When an electron in conduction band from emitter falls into hole in base, it become electron in valence band. I wonder where the electron will go. - the electron now is in valence band and it moves in valence band to positive lead of battery VBE - the the electron now is in valence band and it moves in valence band to depletion region in CB junction and here it gets enery from VCB exits valence band and go into depletion region.