Flying bicycles

Bicycles are taking over the world.

Nowadays, bikes can be used for different purposes. An American Defense Department has developed a folding bike that can be attached to a flying man and as soon he reaches the ground it unfolds and it's ready to ride.

Source: http://bicycling.com/blogs/thehub/2013/02/08/this-week%E2%80%99s-signs-that-bikes-are-taking-over-the-world/

The bicycle of the future

2000 Ecocar modelycle - bicycle designed by Wim Van Wijnen.

Source: http://www.pedrodelgado.com/eng/bicycle/tomorow.html

Steel

Through the centuries, the bicycle has evoluted a lot and, to its evolution, the technological development has contributed a lot. Designs, models, styles, materials, manufacturing have turned the first unpleasant, unsecure, heavy and uncomfortable bicycles into attractive, safe, comfortable, light and fashionable bicycles. 

All these changes tried to please the rider's demands. Today's bicycles are lighter, more comfortable and ergonomic due to the use of new materials.

Steel
Considering the frame the support of a bicycle , great improvements have been made in its materials. The first ones were constucted in steel. In 1970 the appearance of alloy steel permitted mechanic welding and the consequent reduction of labor and cost. Next decade aluminium frames appeared and they become very common. However, alunimium cycle of life was too short and it gave place to steel and titanium which are stronger materials.
In 1990s a new impulse was given and new materials emerged. Carbon fiber was then used to frames and they became lighter and stronger. Most of bicycle components (wheels, brakes, chains) are made of stainless steel. 

Source: http://www.madehow.com/Volume-2/Bicycle.html#ixzz2LlpzupL3