Chlamydomonas reinhardtii is a reference model organism for algal genomics and physiological studies. It is especially interesting to study the evolution of regulatory pathways between algae and higher plants. Additionally, it has recently gained attention as a potential source for biodiesel production. The recent accumulation of RNA-seq data allows researchers to study in detail its transcriptome under different physiological conditions. Up to now these studies had remained fragmented, making necessary integrative approaches based on systems biology. Here we present ChlamyNET a web-based tool for the exploration of a gene co-expression network representing the Chlamydomonas transcriptome under relevant physiolocial conditions.