A separate incident, story, or action, introduced for the purpose of giving a greater variety to the events related; an incidental narrative, or digression, separable from the main subject, but naturally arising from it.
Youth is the period in which a man can be hopeless. The end of every episode is the end of the world. But the power of hoping through everything, the knowledge that the soul survives its adventures, that great inspiration comes to the middle-aged. Gilbert K. Chesterton
You had to be aware that I saw that photography was a mere episode in the history of the optical projection and when the chemicals ended, meaning the picture was fixed by chemicals, we were in a new era. David Hockney