Understanding the detailed mechanisms of photosynthesis has become an ever increasingly important research field, as the community aims to apply the understandings from nature to design elements in organic photovoltaics. This thesis is a comprehensive study of the optical properties and the critical role of phycobiliproteins in the absorption of green light for photosynthesis in cryptophyte algae (Rhodomonas CS24 and Chroomonas CCMP270). Investigations of two different isolated proteins, phycoerythrin 545 and phycocyanin 645, are described in addition to investigating the workings of these antennae proteins within the machinery of intact algae. Steady-state and ultrafast spectroscopies with subsequent global analyses, modeling and quantum mechanical calculations are employed to reveal a detailed picture of energy transfer within the proteins and to the photosystems in the intact algae. Any researcher interested in photosynthesis and energy transfer would benefit greatly from the work presented, as a comprehensive experimental and theoretical guide to understanding energy transfer and light harvesting in these natural systems.