Life is defined by base sequences of DNA, a polymer that carries information on how to make proteins—a building block and a functional unit within living cells. As a first step toward making proteins, DNA is read by processive molecular motors, called RNA polymerases (RNAPs). For example, Escherichia coli, a bacterial model organism, has a genomic DNA of about four million bases, and a few hundreds of RNAPs (each covering about 30 bases) can be detected somewhere on the genome at a given time, creating a situation like cars on the highway. While the dynamics of this molecular traffic is important in understanding the structure and function of the genome, we still lack a clear understanding of how even a few RNAPs work in the genomic context. Experimental results suggested that RNAPs can exhibit collective group dynamics by exploiting dynamic changes in DNA topology. In this talk, I will describe our current understanding of RNAP dynamics in connection with the dynamics of DNA topology. I will also present my current experimental and theoretical efforts to make a complete model explaining the emergence of RNAP group dynamics in the genomic context.