This paper introduces the concept and technology of Application-domain Specific Instruction-set Processor (ASIP). First, VLSI design trend over the decades is overviewed and processors are shown to be expected one of the main components in the System Level Design. Then, the advantage of ASIP over General Purpose Processor (GPP) and Application Specific Integrated Circuit (ASIC) is illustrated. Next, processor hardware description synthesis technology, application program development tool set generation technology, and processor architecture optimization technology are outlined. Then, as an ASIP development environment example, ASIP Meister is explained. Next, an application of ASIP to medical and healthcare is introduced. Finally, the possibility of ASIP as an important component of Multi Processor SoC (MPSoC) is discussed.