I only had one of seven viable eggs hatch, and I had to assist her with her hatch. Eggtopsy revealed 3 fully formed chicks in a fluid filled egg...and 3 fully formed eggs in what looked like a normal egg. Go figure!!! Honestly, I had wanted to candle and assist at the end of 21st day, but since it is my first hatch, I was trying to follow the instructions given on the Learning tab, about NOT INTERVENING! However, I feel like if I had opened the bator and candled them at the end of the 21st day, I may have been able to save the 3 normal looking eggs. Very frustrating. Next time, I will follow my mothering instincts and go ahead with candling and possibly assisting, if needed. Just wanted to put that out there, in case someone was considering intervention the same way I was. I would say, go with what your instincts tell you. The Hatching learning section has a title called Hatching 101, and inside that document she has a link to an article on how to assist a hatch. It was very informative, and next time I'll use it earlier.