How and where do clams and their specie get their shells? Are they born with it or develop these shells?

i'm asking where and how clams get their shells because it occurred to me one day , when there are like billions of them the world over. Where do they get their shells? Born with it, develop it after sometime? What? I really want a definite and factual answer. It's been like eating at me for sometime now. Thanks.

How and where do clams and their specie get their shells? Are they born with it or develop these shells?
The larvai develop their own shells. They produce a protein that captures dissolved minute calium carbonate crystals that are dissolved in seawater. The protein lays these crystallls in an exact predetermined place in the protein and at a very specific angle. this process continues as more protein is laid down in a precise position that eventually controls the overall shape of the shell. Marine scientists are intensely studying the process and its chemistry as it produces one of the strongest composites materials known for its minimal weight, flexibilty and resistance to crack propagation.

\Dan.
Reply:i would say they are born without shells them as they are born they find a shell put it on and then live in it