Understanding and adapting the underlying principles of biological systems to engineering systems have the promise of enabling many new mechatronic systems that can operate in unstructured and uncertain environments robustly and efficiently. This paper first reports a brief survey of recent studies on bio-inspired mechatronic systems and their biological counterparts in respects of locomotion, actuation, sensing, and control. Next, brief highlights of the 20 papers in this "Focused Section on Bio-Inspired Mechatronics" are given. Finally, current challenges and future trends of bio-inspired mechatronic systems are described.