Please help me to understand this situation better. I learned today that some schools hatch the Cornish X or Cornish Cross chicks. I was able to see one of these chicks that had newly hatched out. They are yellow and much bigger than my baby chicks that hatch. I have tried to do research but what I found did not go into great details. Please help me to learn why these birds grow so fast. What kind of chickens are they, where did they come from?