The extracellular environment plays a key role in a wide array of cellular functions including migration, tissue formation, and differentiation. This thesis overviews the design of a molecular sensor to measure cellular forces and a hydrogel system to engineer angiogenic sprouting. We developed molecular force probes (FPs) that report traction forces of adherent cells with high spatial resolution, can be linked to virtually any surface, and do not require monitoring deformations of elastic substrates. FPs consist of DNA hairpins conjugated to fluorophore-quencher pairs that unfold and fluoresce when subjected to specific amounts of force. In chapter two we overview the synthetic strategies to produce these FPs from solid-state synthesis. We then demonstrate the chemical and physical characterization of these FPs. These data show that the FPs can be designed rationally from existing knowledge of the force-responsiveness of DNA hairpins. Chapter three summarizes our methods to affix these FPs to solid substrates to measure cellular traction forces. The silane chemistry to conjugate these FPs to glass coverslips is reported in detail. Then, the results of converting the fluorescence of these FPs to force values is given along with biological validation. We find using this method that cellular tractions are exerted at the distal ends of focal adhesions. In chapter four we present a versatile bioactive PEG hydrogel to study angiogenesis. This material is MMP-degradable and cell-adhesive. We show a microfabrication strategy to micromold these gels to pattern angiogenic sprouting from ex vivo tissue explants.