Research based doctoral programs at various reputed universities in the world play a critical role in the development of human resources in five broad fields (around 41 fields in total) as follows:
Arts and Humanities, Biological Sciences, Engineering, Physical Sciences and Mathematics, Social and Behavioral Sciences.
Today many of the universities especially in North America (USA & Canada) & Europe are well equipped with powerful tools & techniques that empower the graduate student to conduct an extensive research in the field of his/her interest. Though the duration of a doctoral program depends strongly on the field in which it is taken, but normally it takes between three and six years for many of the research areas. Nowadays industry & the academic communities require these researchers to switch between fields as & when it is required.