The code of a cell's gene is read by something called a ribosome, which then helps produce proteins from the genetic code.

Some proteins contain receptors that protrude through the cell wall to receive information from incoming molecules. When an outside substance or molecule docks with the protein receptor, the first step in a protein's signaling pathway is initiated. This signaling starts a cascade of signals from one protein to the next as each protein folds and changes its shape in response to the signaling.

The message ends up reaching the control center of the cell, its nucleus.