One of the basic issues in evolutionary biology is to understand the mechanism(s) underlying the formation of new species, new units of diversity and of evolution. The more advanced the stage of speciation of two diverging populations, the more difficult to delineate the genetic/evolutionary events that has set the process in motion. In this regard, studies on Experimental evolution, wherein populations that are maintained for hundreds of generations in laboratory or controlled field manipulations facilitates to witness the evolutionary changes in real time and may throw light on the processes and patterns of events in nature. Introgressed populations resulting from the interracial hybridization between D. nasuta (2n = 8) and D. albomicans (2n = 6) form the material for the present study. The hybrid populations of these races can be maintained for any number of generations and as of now they have crossed over 700 generations in the environs of the laboratory. These hybrid populations are being maintained in different cages and each one of them is called a 'Cytorace' and there are 16 Cytoraces (C1 - C16). Parental races namely D. nasuta and D. albomicans and the newly evolved Cytoraces (C1 - C16) are grouped together and this cluster is named "nasuta-albomicans complex" - a new taxonomic unit. This 'allosympatric' assemblage of closely related forms has become a goldmine for studies on evolutionary cytogenetics. These cytogenetically closely related members are passing through the process of population differentiation reflecting different patterns of divergence for different sets of phenotypes such as karyotypes, neo-sex chromosomes, morhophenotypes, life history traits, mating behaviour with incipient isolation, Repetitive DNA, isozymes, glue proteins, a few gene loci such as sod1, Rpd3, Aly, and Rab etc. The members of this complex which are at different stages of divergence offer a rare and an unique opportunity to look into multidimensional process of raciation. I will summarize the results of these investigations and also of the ongoing studies and wish to share the pleasure and excitement we experienced during the course of this study.