Is it possible to regrow the hair once they have been lost?

"Lost" as in natural shedding of the hair, or from inherited baldness? In both cases, yes, the hair will regrow.

If it is a natural shedding process (we lose up to 100 hairs a day on average), then the hair will naturally replace itself. If it is inherited baldness or male (female) pattern baldness, one can use Rogaine or Propecia to help regrow the hair, but using these re-growth medications are a life-long committment.

I was referring to inherited baldness. I heard that if the "cell"(dunno what its exactly called...its the thing that holds the hair) has been lost, it can never be grown back.