The Incredible Shrinking Man (1957)

In director Jack Arnold's existential, allegorical science-fiction film about a shrunken, miniscule human being:

• the opening sequence of Robert Scott Carey's (Grant Williams) contaminating exposure to nuclear radiation/waste, when during a vacation off the California coast, his boat came into contact with a strange, misty white cloud above the water and covered his chest with white glittering particles
• his gradually shrinking as he lost weight and stature, compared to his wife Louise (Randy Stuart), and his voicing of his concerns to family physician Dr. Arthur Bramson (William Schallert), followed by numerous tests at the California Medical Research Institute by Dr. Thomas Silver (Raymond Bailey)
• the attack on Scott by his now-dangerous house cat Butch, and his hiding for refuge in a miniature doll house, before he was forced to flee to the basement
• the scene of Louise's fears that the cat ate Scott, with KIRL TV news broadcasting: "From Los Angeles today, a tragic story. The passing of Robert Scott Carey. The report of the death of the so-called Shrinking Man comes from his brother. Carey's death was the result of an attack by a common house cat -- a former pet in the Carey home. Carey was the victim of the most fantastic ailment in the annals of medicine. Thus ends the life of a man whose courage and will to survive lasted until the the very end. A man whose fantastic story was known to virtually every man, woman and child in the civilized world"
• now three inches in height, his retreat into the basement, where he unsuccessfully attempted to snatch a piece of stale cheese from a giant mousetrap; and then his near-drowning (now 3 inches in height) when trapped in the flooded basement due to a busted, leaking water heater
• his deadly battle with a giant spider, with a close-up of its voracious mouth, when he was finally able to impale the threatening creature and kill it

Deadly Encounters
Scary House-Cat Attack	Approaching Spider

• his memorable, concluding enlightened philosophical speech about being infinitesimal (now about one inch in height), as he stood before an enlarged window vent screen: ("I was continuing to shrink, to become... what? The infinitesimal? What was I? Still a human being? Or was I the man of the future? If there were other bursts of radiation, other clouds drifting across seas and continents, would other beings follow me into this vast new world? So close - the infinitesimal and the infinite. But suddenly, I knew they were really the two ends of the same concept. The unbelievably small and the unbelievably vast eventually meet - like the closing of a gigantic circle. I looked up, as if somehow I would grasp the heavens. The universe, worlds beyond number, God's silver tapestry spread across the night. And in that moment, I knew the answer to the riddle of the infinite. I had thought in terms of Man's own limited dimension. I had presumed upon nature that existence begins and ends is man's conception, not nature's. And I felt my body dwindling, melting, becoming nothing. My fears melted away and in their place came acceptance. All this vast majesty of creation, it had to mean something. And then I meant something, too. Yes, smaller than the smallest, I meant something, too. To God, there is no zero. I STILL EXIST!")