With the rapid development of power electronics technology to encompass reduced environmental impact, there is a clear tendency that high and low voltage have seen the proliferation of DC microgrids and its implementation for transmission and distribution in transportation systems, namely all/more electric aircrafts (A/MEAs) and shipboard systems. Moreover, DC architecture is considered as one of the most promising candidates for transportation electrification due to the potential advantages such as higher efficiency compared to AC, less weight of harness, absence of reactive power related issues and also reduced costs. However as compared to the traditional onboard power generation schemes, the recent trends in electrification also bring many design and control challenges. The aim of this tutorial is to identify these challenges and share with the audience (intermediate level) the instructors' industrial and academic experiences in the field. First of all, a detailed framework of industrial and transportation applications of DC microgrids in the real world will be provided. Further, the control and design challenges with electrification in the transportation sector will be addressed. Finally, a detailed study on investigating a primary concern, i.e., cyber security in DC microgrids will be carried out highlighting its critical vulnerabilities concerning system instability/shutdown.