In recent years, the introduction of servers for AI applications has been remarkable, with significant technological innovations from server and GPU vendors, making scalable cloud services and high-performance on-premise HPC environments essential. On the other hand, the increasing performance and density of IT equipment have led to greater heat generation than ever before, highlighting the challenge of heat dissipation in data centers. There are concerns that the cooling methods using air cooling will reach their limits due to the increase in heat generation from further advancements in semiconductor technology and higher density. Therefore, alongside the further development of cloud services and HPC servers, there is a demand for reducing power consumption and operating data centers with efficient heat dissipation to achieve sustainable data centers. This will explain the initiatives regarding immersion systems, water cooling, and liquid cooling systems.