How long does it take a new hair to grow?

How long after a hair falls out does it usually take for another hair to appear on the surface of the skin?! Is it really immediately? Does it take a month?

If you are talking about a transplanted hair immediately after the surgery, it takes between 1-5 months for it to come back and grow. If you are talking about your regular hair that sheds and goes into a sleep cycle, the cycles usually take between 2-6 months as the growth cycles vary between male and female and the age of the person. The younger you are, the more infrequent are the hair cycles and the longer is the growth phase of the cycle.