It depends which molecules you are interested in.
Molecule is a general term that refers to anything made up of more than one atom, so this includes fats, sugars, proteins, and nucleotides (the four major types of molecules in the cell). Specific molecules from each of these categories will be involved in development and maintenance within the cell. For example, DNA encodes the information needed to make proteins, some of which turn on signaling pathways (made up of other proteins and different molecules) to cause the cell to "differentiate" - this means the cell takes on the characteristics that make it a skin cell vs heart cell vs brain cell, for example.
Everything is made of atoms and molecules. Our food is made of molecules and a few salts that bring things like iron [Fe] and potassium [K] into our bodies. Food molecules include protein, fats, starches, and sugars.
Here is a link. Lipids are fats. Nucleic acids are molecules in our food, too.