What do molecules combine to form?

Molecules combine to form cells, which are the basic structural and functional units of living organisms. Cells are composed of various molecules, including proteins, lipids, carbohydrates, and nucleic acids. The combination of these molecules is essential for the cell's functions, such as energy production, structural support, and the ability to replicate and respond to the environment.

On a larger scale, cells group together to form tissues, but the immediate product of molecular combinations at the cellular level is the cell itself. Atoms, which are the smallest units of matter, combine to form molecules, so this option does not apply to the question. Additionally, tissues are made up of cells, while organs consist of multiple tissues working together; hence, combining molecules directly forms cells, rather than these other levels of biological organization.