Which element of a vacuum tube regulates the flow of electrons between cathode and plate?

In a vacuum tube, the cathode emits electrons and the plate (or anode) collects them. To regulate this flow of electrons, a wire mesh called the control grid is placed between the cathode and the plate. By changing the voltage applied to the control grid, the tube can control the number of electrons reaching the plate, allowing it to amplify signals. A small change in the grid voltage causes a large change in the plate current. Other grids, like the screen grid and suppressor grid, are added in more complex tubes (tetrodes and pentodes) to overcome specific issues like interelectrode capacitance and secondary emission, but it is the control grid that primarily regulates the main electron flow.