The theory of domination and (1,2) - domination in graphs is a rich topic of investigation both from the point of view of theory and application. Computer science is a branch in which the use of product graphs has become indispensable, specifically, in problems such as load balancing for massively parallel computer architectures.The aim of this book is to introduce (1, 2) - domination in three types of harmonius graphs and prove the domination number of ladder graphs is less than or equal to (1, 2) - domination number. Also we prove that (1, 2)- domination is notpossible in tetrahedral graphs.