Digital Metamorphosis
Digital Metamorphosis refers to the ability of an FPGA to physically change its function. This is different then what a microcontroller does. A microcontroller can perform different functions, but it does this by sequentially executing instructions that are defined by a program. Those instructions are performed by hardware structures that are set in stone and cannot be changed. An AVR or PIC microcontroller is always going to have the same UART, SPI, and other hardware structures that you are stuck with.
An FPGA is different because it can completely change its hardware structure. With one bit file it can be an AVR microcontroller with all of the UART and SPI peripherals of the AVR. While with another bit file it can become a PIC with all of the standard PIC peripherals. Where things really become interesting is that all of this is defined by HDL code, so you could make a third bit file that would define a AVR microcontoller that implements all of the PIC peripherals!
The sky is the limit, you can make hybrid microcontrollers that have the features you have always dreamed of. Our you can make changes to the peripherals to speed them up or extend their functionality. Either way, you are not locked into any particular hardware design.