The integrated function of the human brain allows every individual human to have unique thoughts, perceptions, memories, and actions. These complex abilities arise from the interconnected neurons in the brain, which acquire information about the world, integrate it with ongoing knowledge and motivational states, and drive subsequent decisions and actions. To mechanistically understand how our brain accomplishes these incredibly sophisticated functions or even one day simulate our brain on a computer is one of the grand challenges of our time. This is a daunting task that requires a comprehensive understanding of a brain at every level of complexity, from molecules to neurons, circuits and systems they form, and the underlying computational principles. Compared to the human brain with approximately 86 billion neurons and 100 trillion synapses, the brain of the nematode worm Caenorhabditis elegans has only 302 neurons and several thousand synapses. To reach the ultimate goal of solving our brain, we must first be able to understand and model much simpler brains. At the scale of C. elegans, scientists were able to map the physical wiring of the entire nervous system – the connectome – in the attempt to reconstruct the worm brain. It soon became clear, however, that structure alone did not solve function. Without the knowledge of the cell-type specific biophysical properties of individual neurons and the activity patterns they produce, theorists were unable to generate a unifying model that explained how the “simple” worm brain works. The Liu lab aims to address this problem by comprehensively characterizing biophysical properties of every C. elegans neuronal cell type and constructing highly constrained single-neuron and circuit level models. The long-term goal of the Liu lab is to biophysically map the entire worm brain, reproduce neural activity patterns in different neuron types and neural circuits, and eventually simulate how the worm brain generates behaviors.