Room cooling is an ineffective approach for next-generation data centers. Latest generation high density and variable density IT equipment create conditions that room cooling was never intended to address, resulting in cooling systems that are inefficient, unpredictable, and low in power density. Row-oriented and rack-oriented cooling architectures have been developed to address these problems. This paper contrasts room, row and rack architectures and shows why row-oriented cooling will emerge as the preferred solution for most next generation data centers.