Biological circuits (biochemical circuits within a cell and neural circuits) appear to be complicated. The work in my lab has been motivated by the following questions: how many degrees of freedom do these circuits have? By attempting to control the dynamics of different parts of such circuits, can we control animals behavioral decision or a cell's developmental choice? And through such attempts at control, can we gain a better understanding of the architecture of the underlying circuits? In this talk I will describe our attempts at controlling the behavior the nematode Caenorhabditis elegans and ask if we can trigger neural activity patterns in the animal to make it believe that there is a chemo-attractive signal gradient in its environment. In the process, I will also describe novel hardware and software tools that make our experiments possible.