let me give it a try,
When a cell in not replicating, in interphase stage that is, It has 46 chromatins. these are long and thin and are not easily visible. Each Chromatin is one strand of D.N.A. So when the cell is receives signals to divide, each D.N.A molecule (each Chromatin) replicates and forms two D.N.A helices one in each of two chromatids joined at the centromere (so each chromatin splits in two chromatids). Each chromatid contains an identical copy of D.N.A and two sister Chromatids (that is containing the same D.N.A) joined at the centromere form a chromosome. So each chromosome contains two chromatids each with a D.N.A helix making each Chromosome to have 2 D.N.A helices.
