The communication was not easy in those days and his work could not be widely publicized. His concept of genes as stable and discrete units that controlled the expression of traits and of the pair of alleles that did not blend with each other was not accepted by contemporaries as an explanation for the apparently continuous variation seen in nature. Mendel’s approach of using mathematics to explain biological phenomena was totally new and unacceptable to many of the biologists of his time. Though Mendel’s work suggested that factors were discrete units, he could not provide any physical proof for the existence of factors and what they were made of. A Punnett square is a graphical representation of the possible genotypes of an offspring arising from a particular cross or breeding event.