Most of the discussion here of minerals and metals is about materials that are chemically one substance. Advanced materials, however, are often created from two or more input substances. This may be an alloy or solution in which the atoms of the inputs mix, or it may be a composite. A composite material is made up of substances that are only physically combined, not chemically.
A solution is usually a liquid (a "solvent") into which another gas, liquid, or solid is mixed. The second substance dissociates into its constituent atoms or molecular fragments. The two substances mix chemically. The result is usually still recognizably the solvent, but with some chemical differences.
A familiar example of a solution is salt in water. About 400 grams will dissolve in 1,000 grams (1 litre) of water. This amount increases slightly with water temperature; the increase is much greater for some solids. Saltwater behaves differently from pure water in a several ways. It has a lower freezing point and a higher boiling point, it is electrically conductive, and so on. But, saltwater is recognizably water.
Water is actually the best well-known solvent. It is, in fact, called "the universal solvent" with some exaggeration. Some things that water will not dissolve are managed by alcohol instead. This is why rubbing alcohol and similar substances are used in cleaning.
An alloy is like a solution in which a (usually) metal dissolves into another metal. Not all metals mix as alloys, but human history is filled with discoveries of better alloys. One of the earliest is bronze, an alloy of tin into copper. As an important nonmetal, carbon or coal dissolves into iron to form steel.
Superalloys are metal alloys designed for extreme environments.
Superconductors are exotic materials with zero electrical resistance.
A composite is a material in which two or more materials are combined physically without chemically reacting. A composite is better than the sum of its parts. It may be a laminate formed of two or more layers. It may be solid particles of one or more kinds bound together in an adhesive. It may be a strong structural material covered in a protective material.
Biocomposites are biodegradable or sustainable substitutes for other materials.
Carbon fiber is a strong and lightweight material woven from carbon thread.
Concrete is the mundane building material that surrounds our urban life.
Optical fiber is a thread or fiber of glass that transmits light.