If you look closely at today's picture you can see the "O" on the eggs. But if you look at yesterday's it has an "X". Before  I put the eggs in the incubator I marked one side with an "O" and one side with an "X". This is so I can make sure that I turn them in the morning and at night so that the baby chicks develop correctly. It also helps me make sure all parts of the egg are getting the same amount of warmth.