As a graduate student, Block picked apart the adaptationkinetics involved in bacterial chemotaxis. As an independent scientist, Block has pioneered the use of optical tweezers, a technique developed by Arthur Ashkin, to study biological enzymes and polymers at the single-molecule level. Work in his lab has led to the direct observation of the 8 nm steps taken by kinesin[2] and the sub-nanometer stepping motions of RNA polymerase on a DNA template.[3] While consulting for the United States government through JASON, Block has researched the many threats associated with bioterrorism and headed influential studies on how advances in genetic engineering have impacted biological warfare.[4]