for - trees are stronger than steel

biomimicry - trees - (see below)

• strong tubular cells in
  • the trunk and
  • branches
• grow and knit themselves into concentric tubular layers one on top of the next, every season.
• That is why you can count the rings on a tree to determine its age.
• This concentric, circular structure is the reason, that for its weight,
  • wood is still the strongest building material on the planet.