Small-form-factor computing today is offering embedded computing systems designers a wide variety of options for using high-performance embedded computing in small space, as well as adding I/O, memory, specialized computing, and many other kinds of computing functionality. These small-form-factor boards can come in standard form factors like PCI Mezzanine Card (PMC), COM Express, Switched Mezzanine Card (XMC), and FPGA mezzanine card (FMC). These small-form-factor and expansion cards offer unparalleled flexibility to systems designers, and enable manufacturers to respond quickly to rapidly changing customer needs. Options for mezzanine card form factors and interconnects also are expanding, often in parallel with established open-systems industry standards like OpenVPX. Many of these options involve rugged solutions to help small-form-factor boards deal with environmental extremes such as shock, vibration, temperature, and humidity. These new mezzanine card options help designers respond to perhaps the most important concern for embedded systems -- small size, weight, power consumption, and cost SWaP-C).