**2. Building blocks and matrix**

### **2.1. Cells**

Cells are building units of tissues and organs and tissues are the basic unit of function in the body. In general, cells secrete their own support materials and structures, which are called an *extracellular matrix*. This matrix, or scaffold, is supporting the cells; it also performs as a relay station for a number signaling molecules [2].

#### **2.2. Messages/signals**

Cells acquire messages through multiple sources that grow available from the local environment. Each signal can enhance or initiate a series of responses that decide what will happen to the cell. By understanding how individual cells react to signals, interact with their surrounding environment, and organize them into tissues and organisms, researchers can manipulate these processes to repair damaged tissue or even create new cells.

**Figure 2.** A view of a eukaryotic gene, its control elements in the DNA and the proteins that guide the RNA polymerase to the correct starting point for transcription [3].

In all organisms, a *DNA-dependent RNA polymerase* is performing the production of mRNA for protein synthesis or the various non-coding RNA molecules that are used in the cell. *Transcriptional control* is the main method to control what proteins (and nucleic acids) are produced in the cell, and in what amounts (**Figure 2**).
