Yes they are, an organ is made of several types of tissue and therefore several types of cells. For example, the heart contains muscle tissue that contracts to pump blood, fibrous tissue that makes up the heart valves, and special cells that maintain the rate and rhythm of heartbeats
It is stated in the Unified Cell Theory by a Botanist named Schleiden and a Zoologist named Schwann that all Living Things (organisms) are composed of 1 or more cells. The cell is the basic unit of life.
