Our Universe is made of particles – the smallest, most indivisible building blocks of our world are particles. – No, not any more!!
The world is made of extremely small vibrating loops called ‘strings’ and they must vibrate in 11 dimensions to properly constitute the Universe. The String theory says this. A string is one-dimensional contrary to the elementary particles which have no dimensions. Now the different ways the strings vibrate give particles their unique properties. That’s why a book is different than a tree.