A transistor comprises a pair of source/drain regions having a channel region there-between. A transistor gate construction is operatively proximate the channel region. The channel region comprises a direction of current flow there-through between the pair of source/drain regions. The channel region comprises at least one of GaP, GaN, and GaAs extending all along the current-flow direction. Each of the source/drain regions comprises at least one of GaP, GaN, and GaAs extending completely through the respective source/drain region orthogonal to the current-flow direction. The at least one of the GaP, the GaN, and the GaAs of the respective source/drain region is directly against the at least one of the GaP, the GaN, and the GaAs of the channel region. Each of the source/drain regions comprises at least one of elemental silicon and metal material extending completely through the respective source/drain region orthogonal to the current-flow direction. Other embodiments are disclosed.