In the junctionless transistor [1] the doping type and concentration in the channel region is essentially equal to that in the source and drain, or at least to that in the source and drain extensions. This paper will first focus on the Revolution of the junctionless transistor, concentrating on the initial reports and studies in 2009. Then the Evolution of the junctionless transistor will be discussed since those early reports in 2009. A variety of studies will be reviewed, as junctionless transistors are being reported in many more materials other than Si, such as in Ge and InGaAs, and very recently in MoS2 and in other transition-metal-dichalcogenide semiconductors.