Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.

Here, we show that the development of nuclei and subsequent growth of a molecular organic crystal system can be induced by electron beam irradiation by exploiting the radiation chemistry of the carrier solvent.

Non-classical crystallisation (NCC) pathways are widely accepted, however there is conflicting evidence regarding the intermediate stages of crystallisation, how they manifest and further develop into crystals. Evidence from direct observations is especially lacking for small organic molecules, as distinguishing these low-electron dense entities from their similar liquid-phase surroundings presents signal-to-noise ratio and contrast challenges. Here, Liquid Phase Electron Microscopy (LPEM) captures the intermediate pre-crystalline stages of a small organic molecule, flufenamic acid (FFA), a common pharmaceutical. High temporospatial imaging of FFA in its native environment, an organic solvent, suggests that in this system a Pre-Nucleation Cluster (PNC) pathway is followed by features exhibiting two-step nucleation. This work adds to the growing body of evidence that suggests nucleation pathways are likely an amalgamation of multiple existing non-classical theories and highlights the need for the direct evidence presented by in situ techniques such as LPEM.

A new class of deep eutectic solvents are presented which exhibit all of the physical characteristics of classical deep eutectic solvents, with the exception that one of the components is volatile when exposed to the atmosphere at room temperature. This enables a premeditated, auto-destructive capability which can lead to novel crystalline identities. We demonstrate the effectiveness of this concept through the room-temperature crystallisation of a broad range of organic molecules, with a particular focus on pharmaceuticals, that possess a variety of functional groups and molecular complexity. Furthermore, we show how, through the simple altering of the eutectic composition, polymorphism in paracetamol can be controlled, enabling the elusive metastable form II to spontaneously crystallise at room temperature.Born from the class of solvents known as ionic liquids, the deep eutectic solvents (DESs), named from the Greek "εu" (eu = easy) and "τήξις" (teksis = melting), have been an increasingly well-researched class of solvents for the last two decades. They have been a boon to catalysis, extraction processes, electrochemistry, organic synthesis and in the creation of more efficient batteries and dye-sensitized solar cells. [1][2][3][4][5][6][7] Originally conceived as a greener and cheaper alternative to the more toxic and less environmentally friendly ionic liquids, 8,9 DESs Supporting Information Table S1 and Figures S1 -S21 Accession Codes CCDC 1879336 and CCDC 1879689 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.