Basic Tissue Types. All of the various tissues of the human body can be categorized into four basic tissue types. All organs are built of these four tissues, which have consistent characteristics and arrangements from organ to organ. Thus an appreciation of the major features of these four basic tissue types can greatly simplify your understanding of the cellular composition of the many organ systems. 1  OVERVIEW.
Definition of session for English Language Learners : a period of time that is used to do a particular activity : a formal meeting or series of meetings of a group of people (such as a court of law or legislature)
A school shooting is a form of mass shooting attack on an educational institution, such as a school or university. School shootings have sparked a political debate over gun violence, zero tolerance policies, and gun control. The United States has the highest number of school-related shootings. From 2013 to October 2015 there were 142 school shootings in the United States.