What makes an organism look the way it looks?
It's the genes! A gene is a sequence of molecules on a larger structure called the DNA. There are only 4 different molecules available and their order defines the way an organism looks like. Humans have around 30.000 genes (+/-).There are different types of genes. The most important ones in the context of the look of an organism are genes that code for proteins (the bricks of life). A sequence of 3 molecules on the DNA codes for the synthesis of one amino acid. Several amino acids are put together to form a protein (i.e. a chain of amino acids) and finally such a synthesised protein can be used for various organic building purposes.