In this thesis, I study the properties of cold neutral atoms, including Bose-Einsteincondensates (BEC), inside periodic light-shift potentials created by optical lattices.In the ¯rst part, a new optical-lattice scheme, employing Raman transitions, hereafterreferred to as a Raman Optical Lattice (ROL), is investigated. This optical latticepossesses a novel sub-Doppler cooling mechanism and a reduced periodicity. Boththeoretical and experimental results con¯rm these two characteristics of the ROL.In the second half of the thesis, instead of thermal atoms, optical lattices are loadedwith condensate atoms. Our BEC apparatus and the procedure towards forming aBEC are described in detail. After the achievement of the BEC, a 1D far-detunedoptical lattice is applied to the BEC. A number of phenomena are observed, includingKapitza-Dirac di®raction, thermal atom interference, atom interferometry, Blochoscillations, and a super°uid to Mott-insulator transition. Finally a brief discussionabout future work is given.xiv