The world around us is not as clean as we considered it should be. Believe it or not, bacteria are everywhere and contaminate “our clean world”. The bacteria are a large group of unicellular, prokaryote, microorganisms. They are ubiquitous in every habitat on Earth, growing in soil, acidic hot springs, radioactive waste, water, and deep in the Earth's crust, as well as in organic matter and the live bodies of plants and animals. There are typically 40 million bacterial cells in a gram of soil and a million bacterial cells in a milliliter of fresh water; in all, there are approximately five nonillion (5×10³⁰) bacteria on Earth, forming much of the world's biomass. It is meaningful to know about these bacteria living in our daily life. And this project will investigate on the bacterial contamination levels on the surfaces we contact frequently in our daily life.  I will select the surfaces that are most related with us. They are including the keyboard of public computers, the teeth brush, the knot of the door, the desks in the library, etc.  After the project, we will get a general idea about how “dirty” the surroundings around us.