Could you recognise yourself in a picture? Let's try:
THIS IS YOU!
Or rather, lots of these are you.
Did you know you have more bacterial cells in your body than human cells? The ratio is 10 bacterial cells for each human cell, according to the NIH Human Microbiome Project, you can be accurately described at as a planet for these creatures. You cannot communicate with them directly, but the chemical transactions of a diverse microbiota keeps your body healthy, while an imbalance of their populations (if you have too many of a single kind) can make you sick (e.g. Helicobacter pylori have normally inhabited humans throughout human evolution and are still found in the vast majority of humans with no negative symptoms, but they can also contribute to gastrointestinal diseases). Keeping a healthy diversity of inhabitants is the reason why probiotics are good for you and why you should never use antibiotics/antibacterials needlessly.
Zoom out. Bacteria, archaea, and fungi inhabit your different tissues. Tissues are like ecosystems, each and every one of them. Some are more conducive to certain kinds of microorganisms than others. The skin on our forehead does not have the same conditions as that inside our nostrils or our mouths (a.k.a. the Amazon rainforest of the head for microorganisms). In many tissues, such as those in your digestive tract, these microorganisms are essential for your health. Sadly, our knowledge of the roles that these microorganisms play in our bodies is still in its infancy. For example: we know women's hands have a greater bacterial diversity than men's hands, but we don't know why.
Zoom out. Tissues conform organs. Very different conditions in each and many of their inhabitants cannot thrive in other environments. Those that live in your toungue are different than those that live in your stomach, which are different than those that live in your intestines (wash your hands to keep it that way!).
Zoom out: Organs are strung together in systems. For example, your stomach is part of your digestive system, but other organs are part of the cardiovascular system, endocrine system, nervous system, excretory system, immune system, etc. Each system fulfils crucial functions that keeps the organism as a whole alive. Systems themselves affect each other: energy and chemicals flow from one organ to the next and regulates their functioning. What happens on one part of the organism has an effect across the entire organism as these systems maintain the cohesiveness of the organism as a single "self".
Zoom out. Functional organs maintain the unity of a (multicelular) organism. You can get a visual of the human organism if you check a mirror. A basic test for "self awareness" is the mirror self-recognition test (MSR). Many animal species pass this test, including apes, elephants, dolphins, several bird species, and even ants. Humans are not born with this capacity, but they tend to develop it around 18-24 months of age. Check your nearest mirror to see if you pass the MSR test.
Zoom out. The human organism is a social animal. Like ants, bees, and termites, humans depend on other humans to survive. No two are alike and different humans do different things that help keep other humans alive. Humans tend to clump together to facilitate this. We call them "villages", "towns", or "cities", depending on the size. Much like biological organisms, a city's material and energy flows (a.k.a the urban metabolism) are dependent their size. For example, studies show that the larger the city is, the faster its inhabitants tend to walk.
Zoom out. Cities live in a matrix of other environments (ecosystems) defined by of both living and non-living components and their interactions. Even if these ecosystems are not dominated by humans, they are still crucial for their survival. Energy and chemical flow from one environment to the next in endless cycles. The river keeps forest alive and viceversa. Just think: where does your, water and your food come from? Where does your liquid and solid waste go? And no, the right answer is not, "the faucet, the supermarket, the toilet, and 'some truck picks it up' ".
Zoom out. Ecosystems themselves are linked together in biomes. Where you draw the line is arbitrary, since it is all connected, but the conditions in biomes are drastically different from one another (compare a desert, to a forest, to a tundra), and yet each fulfil crucial roles that keep the planet organism alive. What happens on one side of the world is felt everywhere because air and ocean currents connect biomes together. For example, most oxygen in the air you breathe came from marine algae. They are not just for sushi.
Zoom out: As far down into the lithosphere and as high up into the atmosphere as we have been able to measure, we find life. All these biomes liked together make up a planet. We call this one "Earth".
When astronauts take a glimpse at the planet organism from outer space, they experience euphoria, exhilaration, ecstasy. They call this cognitive shift of awareness "the overview effect". It is the Earth looking back and recognising itself, much like you did in the mirror. Narcissistic? Perhaps. But like toddlers turning two years of age, it is time we grew up/evolved, looked hard and recognised ourselves.
You are beautiful.
You are a planet.
Now start acting like one.
Bonus: Starting with a bacteria and ending with the planet was an arbitrary decision. What is beyond?