When sugar and salt are dissolved in water, they become invisible. This is because the individual sugar and salt molecules are too small to be seen by the naked eye.

Here's a breakdown:

* Sugar: When sugar dissolves, it breaks down into individual sugar molecules. These molecules are surrounded by water molecules, effectively hiding them from view. The solution appears clear and colorless.

* Salt: Salt dissolves in a similar way. The salt crystal breaks down into sodium and chloride ions, which are surrounded by water molecules. The resulting solution appears clear and colorless.

Important Note: While the dissolved sugar and salt molecules are invisible, the solution itself may take on a different color depending on the concentration of the solute. For example, a very concentrated sugar solution may appear slightly yellow, while a very concentrated salt solution may appear slightly cloudy.