How do molecules pass through the cell membrane?

Hint: The cell membrane is one of the super multi-tasker of the body.
It provides a varied structure for the cell, protects cytosolic contents from the environment and also allows cells to act as specialized units.

Complete answer:
A membrane is the cell’s outer box with the rest of the observable substances. There are various processes either by using energy (active) or without energy (passive) which a molecule can pass the cell membrane. These processes that may included:
-Diffusion – simple and facilitated
-osmosis
-Active uptake
-Endo and exocytosis

Diffusion: It is a type of passive cell transport. In diffusion, various molecules move from areas of high concentration to areas of low concentration in order to decrease the concentration gradient. Diffusion from areas of low concentration to areas of high concentration does not involve energy to occur.
Osmosis: osmosis is a process by which the molecules of a solvent pass from a solution of low concentration to a solution of high concentration through a semipermeable membrane.
Active Uptake: It is defined as a process that involves the movement of molecules from a region of lower concentration to a region of higher concentration against a gradient or any barrier with the use of energy synthesized from ATP.
 Endocytosis and Exocytosis: These are two processes by which cells move materials into or out of the cell that are very big to directly pass through the lipid bilayer of the cell membrane. Large molecules, microbes and waste products are some of the substances moved through the cell membrane via this process.

Note: Cell membranes are semipermeable that means they allow certain small molecules and ions to passively diffuse through them. Whereas, other small molecules are able to make their way into or out of the cell through carrier proteins or channels. It is during these instances that bulk transport mechanisms are needed.