Eli5: How do bones and other organs know what shapes to grown into?

Question

Eli5: How do bones and other organs know what shapes to grown into?

In: 3675

Answer 1

Imagine a crowd of identical people, only differing by age. Now the oldest one, who is in the middle, sprays a perfume. Each person in the crowd follows the same rules: if they smell a lot of perfume, they turn into a heart cell. If they smell a medium amount, they turn into a kidney cell. If they only smell a little, they turn into a liver cell. The person that sprayed the perfume created what is called a “chemical gradient”, which allows the other people to know where in the body they are located. This is one way cells know how to turn into different things and shapes (they “differentiate”).