Home Brew Talk asked me to write a post for them, so I wrote on what I know best: yeast.
The full article can be found here: 3 Common Yeast Misconceptions
Misconception: Yeast growth and cell division only occur at the beginning of fermentation.
Misconception: Yeast activity slows at the end of fermentation because the yeast is exhausted.
Misconception: Water washing yeast removes contamination and dead yeast.