Modular robots (MRs) consist of similar modules that can be configured into different shapes. MRs introduce a number of benefits over conventional robots specifically designed for a task. Self-reconfigurable modular robots (SRMRs) are a sub-category of MRs that can perform complex morphological changes by making use of autonomous attachments and detachments. This thesis is pointing out various aspects of MRs with particular interest in SRMRs (but not exclusively). First of all, designs of SRMRs are studied and improvements have been demonstrated in Roombots (RB), a SRMR designed in the Biorobotics Laboratory. The design improvements involve both electromechanical hardware, control and planning aspects. After all improvements, complex scenarios can be studied involving more than 10 modules adding up more than 30 DOF system. Such SRMRs are not intuitive for humans to operate. To overcome this issue, three different user interfaces (UIs) are proposed covering different aspects to simplify use of SRMRs. The first UI is used for conveying shape information to SRMRs using a tangible interaction interface as a proxy. The second one does not have any interaction medium and user directly control SRMRs via gestures that are tracked by external vision systems. The last UI shows possibility of assembling SRMRs in a virtual reality environment using a head mounted display and a hand gesture tracking system. All three of proposed UIs are novel and first of their kind for SRMRs. The final focus is locomotion with modular morphologies and presented in three major studies. Initially, one of the most simplest modular structures, a parallel chain structure, is studied to develop a goal driven neuro-visual locomotion model of a swimming lamprey robot. It is followed by a slightly more complex chain structure. A snake robot is simulated during different serpentine gaits to evaluate implications of different on-board camera placement strategies for such robots. In the last phase, the importance of compliance in legged locomotion is experimentally assessed for quadrupedal modular structures. Compliance of legs as well as a control scheme that acts as a compliant element is taken into consideration for a comparative evaluation. Locomotion is a fundamental part of all mobile robots. Three biologically inspired methods are offered to tackle locomotion of MRs that present performance improvements on multiple aspects as well as better understanding of certain concepts. Although the idea of modularity is widely used in industrial production and common daily items, MRs still don't find much use in daily lives. This thesis brings MRs one step closer to wide daily use by addressing such systems from multiple perspectives.