Synthetic biology endeavours to apply engineering principles to the design and construction of new biological circuits. At present, our ability to read (sequence) and write (chemically synthesise) genetic information far exceeds our ability to rationally design new biological circuits. However, progress is being made in the design and implementation of circuits of increasing complexity. New circuits may be aimed at solving real world problems or may solely be for the purpose of learning by building, in other words attempting to uncover the design principles behind the operation of biological circuits. Much can be learnt by an iterative process of design‐build‐test‐modify, even on very simple genetic circuits. In this talk I will give an overview of synthetic biology and present some of our recent work, where we have designed, built and tested small circuits capable of exhibiting bistability of gene expression.