 The discovery of SARS-CoV-2 in December 2019 has led to the spread of the virus globally, resulting in over 2 million cases of infection and more than 150,000 deaths as of April 16, 2020. The virus uses the ACE2 protein as a cell receptor to enter human cells, making it essential for understanding how the virus invades human cells. This study examines the expression of ACE2 in various human tissues in order to gain insight into the mechanism of SARS-CoV-2 infection. The results show that ACE2 expression is highest in the small intestine, testis, kidney, heart, thyroid, and adipose tissue, and is lowest in the blood, spleen, bone marrow, brain, blood vessels, and muscles. Additionally, ACE2 expression does not differ significantly between males and females or between younger and older individuals in any tissue. However, in the skin, digestive system, brain, and blood vessels, ACE2 expression levels are positively correlated with immune signatures in both males and females. Furthermore, in the This article was authored by Meng Yuan Li, Lin Li, Yu Zhong, and others. We are article.tv, links in the description below.