The USSJ's

1st reached by Trunks en Vegeta in the Room of Spirit and Time (aka The Hyperbolic Timechamber). This room is the ultimate weapon to train in because 1 day outside is 1 year inside, very handy if you dont have allot of time. 1 of the bad things is that the body ages a year in one earth day. the room is one emty space were temperatures can change drastic. And because the room is nothing but emptyness you can do what ever you want! Trunks and Vegeta were the 1st ones to train in there as Super Saiyans and achieved great power. Muscles grew bigger but speed decreased
The ones who achieved this goal are: Vegeta, Trunks