Abstract: Disclosed herein are molecular markers and assay methods for characterizing cells. As disclosed, the methods entail determining a methylation state of at least one CpG in a region of a nucleotide molecule of the cell, comparing the methylation state with that of a corresponding CpG of a comparison cell of a known cell type, a known cell line, or a known cell strain, and distinguishing, identifying or designating the cell type, the cell line or the cell strain of the cell based on whether the methylation state is the same or different from that of the corresponding CpG.