Multimeric barcoding reagents for labelling a target nucleic acid comprise: first and second barcode molecules linked together, wherein each of the barcode molecules comprises a nucleic acid sequence comprising a barcode region; and first and second barcoded oligonucleotides. The multimeric barcoding reagents enable spatial sequencing. A single multimeric barcoding reagent can be used to label sub-sequences of an intact nucleic acid molecule or co-localised fragments of a nucleic acid molecule. The labelled sub-sequences can be sequenced and the sequencing data processed to determine the sequence of sub-sequences from a single intact nucleic acid molecule or from co-localised fragments of a nucleic acid molecule. Corresponding libraries, kits, methods and uses are provided.