Photosynthesis by marine diatoms generates about 20% of the 100 billion metric tons of organic carbon produced on Earth each year.  They also process about 7 billion metric tons of silicon on a yearly basis to produce their elaborate silica-based cell walls.  These microscopic organisms thus play a critical role in global scale elemental cycling.  Whole genome sequence is now available for two diatoms, Thalassiosira pseudonana and Phaeodactylum tricornutum, with two additional whole genome diatom projects underway.  Our current studies focus on the centric diatom T. pseudonana because of the cosmopolitan distribution of this genus in the world’s oceans.  We use a combination of whole genome transcriptome analyses and targeted proteomics studies to identify the suite of genes of utilized during environmentally relevant conditions.  At least 1800 new genes have been uncovered that do not show similarity to known genes from other organisms.  We have begun targeting these genes to understand essential features of diatoms such as silicon and iron utilization.