*Cytographia* is an elegy for species we will never know, or will never know again, expressed through generative illustrations from an imaginary book about imaginary organisms. The artwork depicts speculative cell structures whose appearances and movements arise emergently and in response to real-time user interactions. *Cytographia* was created using [p5.js](https://p5js.org/) (an open-source programming toolkit for the arts) and may run best in the Chrome browser on OSX. An algorithmic "neoincunabulum of xenocytology", *Cytographia* presents an interactive diagram of a one-celled microorganism, styled to evoke a hand-drawn engraving. Every aspect of this illustration is generated through custom code, including the simulated behavior of the depicted creature, the poiesis of its anatomy, the calligraphic quality of its lines, the asemic letterforms of its labels, and the virtual "paper" on which it is rendered. *Cytographia*'s drawings may be exported as high-resolution PNG images, or in an SVG vector format suitable for pen-plotting on A4 paper. The *Cytographia* project draws inspiration from several historically significant books that visually and methodically documented encounters with the unknown. These include Robert Hooke's *[Micrographia](https://en.wikipedia.org/wiki/Micrographia)* (1665), a landmark of scientific observation in which living cells were described for the first time; Edmund Fry's *[Pantographia](https://en.wikipedia.org/wiki/Pantographia)* (1799), an attempt to compile exemplars of all the world's writing systems; Ernst Haeckel's [*Kunstformen der Natur*](https://en.wikipedia.org/wiki/Kunstformen_der_Natur) (1899), a rich exploration of symmetry and structural hierarchy in natural forms; and Luigi Serafini's hallucinatory *[Codex Seraphinianus](https://en.wikipedia.org/wiki/Codex_Seraphinianus)* (1981), a visual encyclopedia of an artist's imagined world. The generative letterforms in *Cytographia* are loosely based on 16th-century typefaces by [Ludovico degli Arrighi](https://en.wikipedia.org/wiki/Ludovico_Vicentino_degli_Arrighi). *Cytographia* represents a culmination of several enduring threads in Golan Levin's thirty-year *oeuvre* of interactive software art, including research into responsive blobs (e.g. [*Polygona Nervosa*](https://objkt.com/asset/hicetnunc/56312), 1997); artificial life (e.g. [*Obzok*](https://www.youtube.com/watch?v=oVOCKzE2fZk), 2001); the use of physics simulations in computational drawing (e.g. [*Floccus*](https://artbase.rhizome.org/wiki/Q3783), 1999) and the algorithmic generation of asemic writing systems (e.g. [*Alphabet Synthesis Machine*](https://en.wikipedia.org/wiki/Alphabet_Synthesis_Machine), 2002). *Cytographia* requires a modern browser with WebGL and hardware acceleration enabled. The recommended configuration for *Cytographia* is the Chrome browser on MacOS, in which the artwork is known to produce consistent and replicable results. The project responds to both mouse/touch and keyboard interactions. An index of *Cytographia*'s key commands can be displayed by pressing **h** (for "help"). These key commands provide access to functionality including file export; toggles that enable or disable various graphical options, potentially improving performance on some systems; and access to a playful "sandbox" mode, in which a collector or visitor can assemble the organelles of their own imaginary lifeform.