O mankind! Have fear [and awareness] of your Lord, Who created you from a single self, created its mate from it, and then disseminated many men and women from the two of them. Heed Allah, in Whose name you make demands on one another and also in respect of your families. Allah watches over you continually. ( Surat an-Nisa', 4:1)
Allah protects and watches all beings; controls, watches, witnesses, and supervises everything from the stars and solar systems to atmospheric events and to the societies and plants covering this planet, and from the human body's complex and complicated systems to the micro- and macro-universes that are invisible to the naked eye.
People may think that they are not responsible to anyone, and thus may live without a purpose. But regardless of what they are doing, Allah sees them, for nothing can be hidden from His Sight. Allah repays anything done with justice, for He has comprehensive knowledge. Many people think that Allah created the universe and then left it to its own devices. Yet this is only a delusion and an assumption.
Allah knows every invisible cell down to its minute details. While functioning in perfect harmony with the trillions of other cells in the body, one day a cell can no longer control its replication and thus causes cancer. We have no control over such developments, but Allah knows all of this and controls every phase. Just as a person cannot take a step without Allah's will, that cell cannot function without His will. Given that He is the Creator, Allah knows everything and is the sole source of all knowledge. No being can do anything without Him knowing it. One verse reads:
2009-08-19 11:42:15... Allah is watchful over all things. ( Surat al-Ahzab, 33:52)