Imagine you have a big lego castle that you want to make into lots of little lego castles. To do this, you need to take apart the big castle into smaller pieces so you can build more little castles.
Your body is made up of lots of cells, kind of like lego pieces. Sometimes, these cells need to make more of themselves by dividing into two. This is when mitosis promoting factor comes into play.
Mitosis promoting factor is like a special tool that helps cells divide. It tells the cell when it's time to start dividing by making a signal that travels through the cell. This signal tells the cell to start copying its DNA and to make two copies of everything inside the cell. Finally, the message tells the cell to divide into two new cells with the same DNA as the original cell.
Just like taking apart your lego castle, mitosis promoting factor helps your cells divide into new ones. And without it, your body wouldn't be able to make new cells and grow.