When we drive, car navigation know where we are. If we set our destination, it guides us and tells us estimated arrival time. Why can it do that? it can see where we are now by continuing to receive electrical signals from artificial satel…

We usually use chicken's eggs for cooking. Eggs have various structure to make chick's body and protect chick's life until hatching. If you look closely at the yolk, you will see a white spot called an embryo. embryo is the important part …