Microcontroller kits are available from most any electronics component retailer. These devices are so common and so flexible in terms of their usage that there are few industrial, medical, tech or other processes that do not use them to some degree.
Microcontroller kits oftentimes come with everything required to program the microcontroller and, in some cases, they also come with boards that can be used to experiment with the microcontroller itself in various ways. Other kits are designed so that they include all the parts necessary to create a device or component with a microcontroller as one of its primary parts. These include a wide range of different devices that a DIY enthusiast can put together, program and make use of all on their own.