In order for a scorpion to grow, it must molt. Every time a scorpion undergoes a molt it has gotten a little bit larger. A scorpion will molt an average of 6 times until it is fully mature.  After that, the scorpion will cease to molt. 

In order for the scorpion to have a successful molt, it must be humid in the cage, or else the scorpion could get stuck in its old skin and die.

After the scorpion molts it will be a lighter color and will be very fragile, as the new skin is not hard yet.  During this critical time, you should not handle or disturb your scorpion in anyway.  Doing so will could damage your scorpion or stress it out.  Their new skin will be hardened within a few days.

The scorpion will not eat for a few days after the molt, and will probably stay hidden.  Make sure you have secure hiding places for them.