A method for adding cell origination barcodes onto beads is provided. The method comprises: splitting a pool of beads into a plurality of reaction volumes, appending pre-made oligonucleotides onto the beads in the reaction volumes, wherein at least some of the reaction volumes each receive an oligonucleotide that contains a sequence that is different from the other oligonucleotides added to the reaction volumes, pooling the beads and repeating the splitting, appending and pooling steps one or more times to produce a pool of beads that comprise the cell origination barcodes. In the one or more repeats the oligonucleotides that are appended are added to previously appended oligonucleotides to form the cell origination barcodes.