Energy, Environment and Economy are Trilemma we are forced to confront in 21st century. Growth of population, Energy shortage and Environmental issues must be solved simultaneously in a world scale. One of the most urgent tasks is to find out cleaner energy sources for environment and to establish technologies to use these energies more efficiently. Recently new discovery of huge hydrocarbon resources such as methane hydrate is reported. We must be more thoughtful to use this precious gift from the earth. Technology for energy saving is of number one priority to be developed. The development of clean fuel for engines is a new frontier for us which seems to be inevitable to meet future stringent emission regulation. Hybrid electric vehicle has attracted attention because of its high efficiency and cleanliness. This technology is another new challenge for engineers. Change comes always from different area. We engine engineers be open minded and aggressive to accept these new changes.