In this DNA re-sequencing microarray, each row is 488 oligos wide, and there are 320 rows, arranged as 64 blocks. In each block, four oligos represent each of the possible A, C, G, or Ts at each position, and a fifth row serves as a spacer. Both the sense and antisense strands are included, so that every base is represented twice (click here for a magnified view). A 15-Kb array thus includes 8 x15,000 features: the current generation of arrays include two million oligos.