At the DNA level, we have 3.2 billion genetic letters in our genomes. How different are we at that level? The answer is: more than you might think. As we have just noted, we are even more different when we start comparing our epigenomes. But in this chapter we will focus on our DNA sequence. In terms of clarifying the DNA differences between us, it’s the dramatic decrease in the price of sequencing the human genome that is changing the scene so quickly. To obtain the first full human genome sequence cost nearly US$3 billion, but now the price is down to less than U$1,000 – and that’s all happened in less than 20 years. Of course, analysing the results so obtained costs a lot more than $1,000, but these comparisons are done by computers. ‘Bioinformatics’ is the name given to this particular discipline.