Vertical instabilities, buckling, in stellar bars weaken and shorten the bar. This can interrupt the bar-induced gas inflow into the central kpc of a galaxy for ˜ 1 Gyr. The subsequent bar growth in length and in amplitude can lead to a recurrent buckling. The first buckling results in the formation of a peanut/boxy-shaped bulge when viewed edge-on, and the second buckling forms an X-shaped bulge. The secular growth of the bar and the recurrent buckling can lead to important observational corollaries in bar fraction, bar detection, offset dust lanes, bar size-to-corotation ratio, etc.