From The Gay Science, Friedrich Nietzche.
Numberless things which humanity acquired in its earlier stages, but so weakly and embryonically that it could not be noticed that they were acquired, are thrust suddenly into light long afterwards, perhaps after the lapse of centuries: they have in the interval become strong and mature.
In some ages this or that talent, this or that virtue seems to be entirely lacking, as it is in some men; but let us wait only for the grandchildren and grandchildren s children, if we have time to wait, they bring the interior of their grandfathers into the sun, that interior of which the grandfathers themselves were unconscious. Often, the son already betrays the father and the father understands himself better after he has a son. We have all hidden gardens and plantations in us; and by another simile, we are all growing volcanoes, which will have their hours of eruption: how near or how distant this is, nobody of course knows, not even the good God.
—Fragment nine of The Gay Science by Friedrich Nietzsche.