Different sequences of atoms give molecules with distinct shapes. This shape is key to a molecule's properties, e.g., its biological effect when binding proteins. Conventionally, the atomic sequence of a molecule is fixed. This proposal, however, investigates molecules that break free from this dogma. 'Shapeshifting' molecules adapt their atomic sequences to match their surroundings. During this Early Career Fellowship, the project team and I will establish methods to control shapeshifting molecules. We will pioneer their applications in catalysis, drugs, and plastics. We expect to discover rare properties, such as plastics made from molecular networks that spontaneously tangle and untangle, making them uniquely strong and flexible. We will also answer open questions about how shapeshifting molecules adapt when they interact with other molecules, quantifying changes in their structures. This knowledge will allow us to make shapeshifting molecules that mould themselves to match complex biological targets implicated in disease. By the end of the grant, we will have shown how shapeshifting molecules differ from conventional materials. We will have also demonstrated the first of their many possible applications in biology and soft materials. These fundamental, chemical advances establish a new research area that will have broad impacts in biochemistry, materials physics and engineering.