Start by making a hand-held magnifier. Make a square of stiff foil measuring 4 x 4 centimetres. You can cut this out of an aluminium pie tray, for example.
Make a small hole about 1.5 millimetres in diameter in the centre of the square using a nail. Try to make the hole as circular as possible, and rub a candle around the edge of it.
Use a dropper to place a drop of water on the hole. Hold the magnifier close to your eye and look through the water drop at an object.
To make a simple microscope, make a magnifier attached to a stand. The easiest way is to use a piece of stiff foil measuring 3 x 6cm. Bend it half-way along its length, so one half is vertical and the other half is horizontal. Make the hole in the centre of the horizontal section, taking care not to damage the foil.
You can make the stand in lots of different ways, depending on the materials you have available. A wooden block with a nail tapped into it works well.
Use a bulldog clip to hold the upright part of the foil on the nail. Lay a sheet of white paper at the base of the block under the horizontal part of the foil. Use a dropper to place a small drop of water on the hole. Place the object you wish to examine on the paper directly underneath the drop of water. Look through the water drop at the object, and use the bulldog clip to move the foil up and down and bring the object into focus.
In both these experiments the drop of water acts as a convex lens, magnifying the object. You won't get a huge magnification using this water lens, but you should be able to see more detail than with the naked eye.
One famous scientist who used simple microscopes in his work was Antony van Leeuwenhoek (1632-1723). He made his own microscopes in order to find out more about living things. These were better than others in use at the time, because he was highly skilled at making lenses.