There is a point when a solution contains more solute than the solvent can dissolve. This solution is known as asupersaturated solution. You normally cannot see the solute in a solution because it is fully dissolved. You are able to see the solute in a supersaturated solution because all of the solute doesn't fully dissolve into the solvent.
I bet I can bring to mind a supersaturated solution that you have come across in your life. Think about making lemonade. Lemonade contains water, lemon juice, and sugar. Water is the solvent, and both lemon juice and sugar are the solutes. Maybe the lemons you used were extra tart, so you decide to add more sugar to offset the tart taste.
As you continue to add sugar, you will reach the point where the solution cannot contain anymore sugar. If you continue to add sugar past this point, then there will be too much sugar to dissolve into the water. You ended up with lemonade that wasn't sweet enough for you, and it has sugar floating in it rather than dissolved in it.