How much chemistry, biology, and physics have you been taught? It is not reasonable to compress all those subjects into a simple sound bite here. But as a starter - particles form atoms held together by forces (energy), they form molecules, which form into cells, which form into organisms - and humans are a class of organism.
The primary forces are the weak nuclear, strong nuclear, electromagnetic, and gravity. The first three play the major roles on what keep us held together.
At a biological level the protein collagen is the critical substance that holds all our cells together. It is the most common protein in the human body and acts like an adhesive or a cement. If we fail to produce sufficient collagen our cells literally start to come apart and from each other - this is known as scurvy and death follows quickly.
Not quite sure that that was the answer you wanted - your question seems somewhat out of place.
