**4. Equipment**

There is so much commercial equipment for agarose gel electrophoresis, but unfortunately, they are rather expensive for its purpose; for example, tens of electrophoresis tanks are needed at a time in students' practice, but it is sometimes difficult to buy so many tanks at a time. One of the major reasons of this higher cost is that platinum is used as electrodes in the tank. Platinum is a precious and noble metal, which is very stable and never degraded in electrolysis. The second reason is that the buffer tank of the equipment has a special shape. Generally, the bottom face of the buffer tank has an anti-U-shaped structure (**Figure 8**). The third reason is that the equipment is sold with the special power supply. It seems that no electrophoresis is available without the manufacturer's specified power supply.
