This holds an organism's hereditary information. All cells contain the same genetic information before differentiation.

the answer is DNA

DNA or deoxyribonucleic acid is macromolecule composed of nucleotides (nitrogen nucleobase, deoxyribose sugar and phosphate group) which carries genetic information (instructions). Instructions within DNA are for development, growth, reproduction and many other functional roles of an organism.

All of the cells within an organism contain the same genome (full set of DNA-chromosomes). When cells begin the process of differentiation (cells become specified) their genome stays the same, but the gene expression is different (different genes are on or off).