Saiyan Levels.

First there is the regular state of the saiyan where they all have black hair.. except for Trunks.
The second state is called: Super Saiyan(SSJ). This is caused when the saiyan gets really angry out of sadness, for instance when Krillin, Goku's best friend, was killed by Frieza. This actually happens with all of the forms. Changes: Golden hair and gotten much and much stronger. The next one is USSJ, Ultra Super Saiyan. The saiyans get ALOT more muscular and get again pretty much stronger. The downside is that they lose speed. Fourth Form is Super Saiyan 2(SSJ2). The first one to get to this form is Gohan. On this form the saiyans get alot stronger and gain some speed aswell. One of the better forms if you ask me. The fifth form logically is Super Saiyan 3(SSJ3). Again the saiyan gets some stronger. The only one to get to this form is Goku. The last form is Super Saiyan 4(SSJ4). This is the strongest form of them all. Goku and Vegeta both get to this one aswell as the two being fused into Gogeta(SSJ4). I almost forgot about the big monkeys. You know saiyans have a tail, right? Well the one from Goku got cut off at first. These big monkeys are Oozaru and turn into this when seeing a sort of moon. There's two forms of these Oozaru: the regular ones and the Golden Oozaru's. The regular ones are turned into when being a normal saiyan, the Golden Oozaru are uhh when SSJ3 see that one moon. Both Oozaru's are 10 times stronger then the form the saiyans normally are.