They look weird, are dangerous and sometimes even deadly, and they are everywhere! Millions no, trillions of them may be swimming in the waterways, flying through the air or crawling on the ground, even all over our bodies (inside too) at this very moment, but we do not see them. Why? Because they are tiny specks of life that belong to the invisible microscopic world.

These microscopic lifeforms are tinier than the full stop you see here, so, even with perfect eyesight human beings cannot see them with their naked eyes. Algae, bacteria, viruses, fungi, protists all belong to the world of microbes.

You will be amazed to learn that these weird-looking microscopic lifeforms have been around for much longer than we humans have and outnumber us by at least a trillion, trillion trillion times!

They are everywhere, from snowy mountains to the ocean floor and even deep down inside the Earth. And what's fascinating is that they have been there always and we only started to 'see' these invisible creatures and began to really take notice of them after the invention of the microscope.

In fact even the names by which these microscopic lifeforms are identified sound strange because they are only seen by scientists who conduct research into the microworld. When people initially started to explore the micro world using microscopes about 400 years ago, they had been not only amazed but also horrified to discover that Earth was teeming with tiny, weird-looking living creatures. And so these lifeforms which we had ignored all this time came into the limelight because some of them have the power to make us very sick and even kill us.

Microlife plays a dual role in our lives; they could be our enemies or our friends. Just as much as microscopic lifeforms could snuff the life out of us, they could also help us survive on this Earth.

Let's step into the microworld today to at least learn about a few of these invisible creatures. The deeper you go down into it, the smaller the creatures become. The lifeforms differ from one level to the other. The microworld is indeed a bewildering place when it comes to size and form, with some of the lifeforms not even being classed as animals and taking alien forms.

For instance, Hydra is an alien looking life form that lives in ponds and waterways attached to aquatic vegetation. They are the freshwater relatives of corals, sea anemones and jellyfish.

Hydra live in freshwater and spend their entire lives attached to plants. Each one has a ring of tentacles at the end of a slender stalk. They use these tentacles to catch food. Would you believe that this micro organism Hydra grows a tiny bud which becomes a baby, when it feels like becoming a parent? The tiny baby which is stuck firmly to its parent's side shares its stomach, so it has no problem getting food.

However, once it is a few days old, it unfastens itself and creeps away, from the parent. Even though a Hydra's baby manages to do so, the baby of a Volvox, another micro-plant that lives in murky water makes sure its offspring does not escape.

The Volvox may appear as just a small, uninteresting blob to our naked eyes, but under a microscope, it is revealed as a beautiful bubble of bright green cells. The bubble which is made of a kind of jelly has a hollow in its centre and this is where the baby Volvox is kept - out of harm's way. Volvox swim using tiny hairs which they beat like wings or hands. As each adult can have more than one baby, there are several young rumbling inside of them as they go about. Even the young Volvox can produce babies inside their own bodies, and so one Volvox can end up creating a collection of micro-plants that roll around inside the parent Volvox.

Then there are simple organisms which are neither true animal nor true plant, consisting of just a single cell which are called protists. Even though a few of the protists.

Even though a few of the protist are big enough to be visible to the naked eye, the majority are micro-organisms. Didinium is a predatory protist. These free-living carnivores are found mostly in fresh and brackish water environments. Three marine species are also known.

Most micro swimmers move through the water by waving their hairs around. Protists such as Giardia and Euglena have long hairs called flagella. Others, such as Paramecium have short hairs called cilia. Infact, Paramecium has a 'fur coat' of cilia which it uses like oars to move about in ponds and puddles searching for food. This micro hunter which is a tough bacterium moves at one sixth the speed of a snail and yet, it could win a medal at an Microlife Olympics for speed!

Giardia is a protist that swims by beating a set of eight hairs. Guess where it swims? Inside our intestines. It is a parasite that can cause many diseases.

Radiolarians are amoeboid protoza with amazing glass-like exoskeletons. These microscopic predators which are marine organisms are smaller than a speck of dust. Their skeletons are amazing structures.

Tardigrades which are also called water bears are tiny animals between o.1 mm and 1.5 mm. They are multicellular invertebrates found in different environments around the world - from the polar regions to the equator. These micro animals have eight short legs that end in claws. Their favourite food is lichens but according to scientists these tiny creatures can live without food or water for years. They are also capable of withstanding temperatures ranging from - 270 degrees Celsius to + 150 degrees Celsius.

Tardigrades are also able to stop their metabolism and become immortal (state cryptobiosis). In order to enter this state, tardigrades retract their legs and become virtually dehydrated. They lose over 99 per cent of the water in their bodies and replace it with a sugar they synthesize. It's a kind of anti-freeze that protects its cells. During this period it limits further water loss and protects itself in a small ball of wax called a microscopic barrel. It comes back to life when favourable conditions return.

Scientists have managed to keep a tardigrade for eight years in a state of cryptobiosis. It is believed that these creatures can stay in this state for thousands of years because tardigrades found in an ice sheet 2,000 years ago had comeback to life.

Have you ever wondered about the green dust that gets on your clothes or body when you climb a tree or play in puddles of water with the water in a pond? They are tiny algae, plant-like life forms that live by gathering the energy in light.

Chlorella is one such tiny algae which measures about 0.015 mm (0.0006 in) across. They are so tiny that it would take about 70 Chlorella to stretch across a fullstop.

Microlife is most abundant and diverse in the sea. While some organisms live on the ocean floor, many spend all their lives floating.

Ceratium is a plank tonic algae or micro plant which is only 0.5 mm long. When magnified it appears like a spiky helmet. It is said that the Ceratium moves by beating two microscopic hairs called flagella, set at right angels to each other.

Among the micro-plant predators, the radiolarians are considered dangerous. Even though just a few millimetres across, they are surrounded by invisible threads and spikes. They trap anything edible that they touch and mop up millions of tonnes of algae each year.

Well, the world of microbes is full of bewildering creatures and there are many more creatures that we like to introduce to you, especially the dust mites and various bacteria. So, look out for facts on more of these microscopic lifeforms next week.

Facts and Pix: Internet and Microlife

(All pictures are magnified)

Take an elevator ride into the micro world

If you imagine yourself on an elevator ride going down about 9 floors into the microworld, here's what you'll find at different levels....

Level 1 - Water fleas, Hydra and a host of such creatures all not more than 1 mm long live here.

Level 2 - Land of single cells or protist such as Didinium and Paramecium.

Level 3 - Tiny algae such as Chlorella with complex cells like the ones, we humans have in our bodies.

Level 4 - Bacteria or if you prefer, you can call it the world of bugs and germs. Definitely not a place to hang around.

Level 5 - The smallest bacteria - the Mycoplasmas are found at this level. These micro-microbes are said to be the smallest things made up of cells. At just 0.0002 mm across the Mycoplasmas are believed to be the smallest things on Earth to be alive.

Level 6 - It's the virus territory - so watch out. Viruses are like tiny packages of chemicals that come alive when they invade liv ing cells. In fact, as viruses can not live without entering or invading living cells, they hardly qualify to be classed among the other microscopic lifeforms you have met at the other lev els so far. There are different types of viruses and the large ones may be as long as Mycoplasmas, but most of them are only 0.000017 mm across. Viruses are smaller than even waves of light. They do not have any colour of their own. If you see photographs of viruses note that the colours have been added only after the actual picture has been taken.

Level 7 - By this time, it is really difficult to view anything - even the most powerful light microscopes which can magnify objects up to 2000 times (that were used to inspect the Mycoplasma) or the beams of electrons and X-rays used on Level 6 will not show any lifeforms here. In fact, everything at this level is million times smaller than at Level 1 and simply cannot have even a flicker of life. So what we get here are individual chemicals - Macromolecules that are complicated substances such as DNA which contains all the chemical instructions needed to make living things.

Level 8 - No more microbes here. Just simple chemicals like glucose which has only 24 atoms.

Level 9 - The last floor is filled with individual atoms. They are the smallest complete pieces of matter inside living things.