Specialized accelerators are the key for energy efficiency for all future systems. While fixed-function accelerators are the most efficient, the use of reconfigurable accelerators allows the in-field and runtime specialization of functions, combining hardware efficiency with broad flexibility. This course will cover the basics of using reconfigurable technology (FPGAs), and then proceed to describe how it can be used for function accelerator in heterogeneous systems. We will cover full and partial reconfiguration, the necessary support they require, and their limitations. We will also discuss the pros and cons of a spectrum of commercial and research choices for implementing accelerators focusing on the interconnection/communication with the host processor and memory. A hands-on lab will focus on the creation of simple accelerators and linking them to simple applications.