Using methods for low-temperature scanning magneto-optical Kerr microscopy, we directly image the electrical injection and subsequent transport of spin-polarized electrons in lateral ferromagnet/semiconductor devices.@footnote 1@ These structures have metallic ferromagnetic (Fe) source and drain tunnel-barrier contacts at opposite ends of a lightly-doped n:GaAs semiconductor channel. The images reveal efficient electrical spin injection extending out to 120 microns in the GaAs channel, and accumulation of spin polarized electrons within a diffusion length (10 microns) of the drain contact. Both injected and accumulated electrons have the same spin orientation (antiparallel to the contact magnetization). By controlling, in situ, the uniaxial strain applied to the device substrate, we show that the accumulated spin polarization actually flows away from the drain contact (against the net electron current), indicating that these electrons are polarized by spin-sensitive reflection from the ferromagnetic drain contact. Furthermore, we show that the electrical conductance of these devices is modulated by the spin orientation of electrons flowing through the drain, demonstrating that the Fe/GaAs Schottky tunnel barrier contacts function both as electrical spin injectors as well as detectors. These experiments are conducted in a geometry that is sensitive only to electron spin precession, allowing for detailed modeling of spin transport in the channel. @FootnoteText@ @footnote 1@ S.A. Crooker, M. Furis, X. Lou, C. Adelmann, D.L. Smith, C.J. Palmstrom, and P.A. Crowell, Science v309, p2191 (2005). This work was supported by the DARPA SPINS and Los Alamos LDRD programs, ONR, and the NSF MRSEC program under DMR 02-12032.