The μMACS One-step cDNA Labeling Kit facilitates fast and effective mRNA isolation and cDNA synthesis, labeling, and purification, without prior preparation of total RNA. Pure mRNA is directly isolated from cells, tissue, or blood, by magnetic labeling with μMACS Oligo(dT) MicroBeads. Due to the fast reaction kinetics the small (50 nm) μMACS Oligo(dT) MicroBeads instantly bind to mRNA molecules and allow for efficient and reproducible isolation of high-purity mRNA. mRNA isolation as well as subsequent cDNA synthesis, labeling, and purification take place in the same column thus reducing loss of material and increasing the sensitivity of microarray based gene expression analysis.