What is the invention which impacted on the world most? In today's world, with the growing technologies, the investments became more high qualities, such as small, light and faster. Some people state that the most important investments in these days is global transportations which gives us more opportunities to travel more faster and to visit more varieties of places in the world. Other people might say that is a computer which gives us the way to do calculation aster and to connect societies all over the world. Even though the great number of investments exists in contemporary word, I personally convinced that the world most important investment is the smart phone. I give several examples and ideas to support my ideas. First of all, the merits of smart phones are their great number of functions that it possesses. Needless to say people can send massages and call to others with smart phone, but also there are many functions: such as voice record, music library, time peer. Furthermore the phones offer many kinds of unique and convenient applications. For example, one of the unique applications, which called cook pad, show and teach information for the food recipe. As I am living alone, this applications often helps me a lot to create new kinds of dishes that I have never cooked. There are so many applications and still they are published new applications day by day. Therefore it is likely to find the applications that you might like. In addition, if we try to have all kinds of those applications without smart phones, the material total weight would be so many that we could not carry them in daily life. Thus, smart phone also help us to live in a convenient life. Moreover, the smart phones play a great roll for connecting people all over the world. I It is true that computers have such kinds of functions, which is internet, however because of their size and weight ,computers are not easy to bring with us in the daily life. On the contrary, the size of smart phones are usually pocket size that people can bring with anytime they want. This makes people get closer and obtain more opportunities to communicate each other without carrying heavy computers. In conclusion, it is true that smart phone have possibilities that we will be addictive users for their great functions, however I personally convinced that demerits are out weight for its merits. Above the reasons I recommend the smart phone is the vest investments in the world.