Implantable medical devices (IMDs) have restored viable and meaningful lives to millions of people who would have otherwise continued to be severely restricted or suffered early death due to their pathologies. Research and development of IMDs are complex and time-consuming and market authorisation is regulated by country laws and regional regulations to provide safe, effective, and reliable products to patients. Due to their invasive nature, IMDs are considered to be high-risk devices that require extensive preclinical research and testing. Current early development phases and their associated requirements are reviewed.