Cells of all kinds share certain structural features. - Albert L. Lehninger

The first living organisms on Earth doubtless arose in an aqueous environment, and the course of evolution has been shaped by the proper­ ties of the aqueous medium in which life began.

The upper limit of cell size is probably set by the rate of diffusion of solute molecules in aqueous systems.

In thermodynamic terms, formation of the solution occurs with a fa vorable free-energy change: ΔG = ΔH - TΔS, where ΔH has a small positive value and TΔS a large positive value; thus ΔG is negative.