Domain: Natural Science — Biochemistry & Molecular Biology
Target concept: Cells stained with fluorescent dyes switch from a dark state to an illuminated state under excitation light.

Video generation prompt: Microscopic view of cells cultured on a glass slide, subjected to fluorescent staining. Recording begins under white-light illumination; partway through, the illumination is switched from white light to excitation light, with the camera holding the same field of view throughout.

Evaluation guide:
(i) Target concept: Fluorescence activation via selective excitation wavelength switching in fixed, stained biological specimens.
Minimum mechanism: A fluorophore must be present in cells; excitation light must match its absorption peak; emission must occur only during excitation and cease immediately after; specimen must be static and optically immobilized.
(ii)Storyline: [Phase 1: White-light baseline] Fixed microscopic view of glass slide showing unstained-looking (dark) cultured cells against uniform background. [Causal transition: Illumination switch] No movement, no zoom, no cut; only light spectrum changes. [Phase 2: Excitation-light response] Same exact field reveals identical cells now emitting uniform, chromatically coherent fluorescence; no cell motion, no shape change, no background activation; brightness difference is absolute and binary (off/on), not gradual or partial.

Manual:
Experimental Procedure
1. Place cultured cells on clean glass slide and apply fluorescent dye.
2. Mount slide on microscope stage; observe under white light illumination — cells appear dark/non-fluorescent.
3. Switch illumination to appropriate excitation wavelength — same field-of-view now shows cells brightly fluorescing.
Observation of Experimental Phenomena
Under white light: cells are dark, low-contrast, and indistinguishable from background.
Under excitation light: cells emit bright, color-specific fluorescence while background remains dark; identical cell positions and morphology preserved.
Summary of Experimental Principles
Fluorescent dyes absorb excitation light and re-emit photons at longer wavelengths; in absence of excitation, no emission occurs — hence dark state under white light (which lacks sufficient intensity at excitation wavelength).

Prompt Grounding rubric:
level_1: No glass slide is shown; no cells are visible on it; there's no depiction of an illumination switch; the camera does not hold a single fixed microscopic field of view; the scene is unrelated to a microscope shot entirely (e.g. a lab bench, a hand holding equipment, or an abstract graphic).
level_2: A glass slide is shown but it's empty or holds only unidentifiable debris rather than cells; the illumination never visibly changes from one type to another; the field of view zooms or shifts substantially partway through; there is no clear before/after moment showing an illumination switch in the same view.
level_3: A glass slide with visible cells stays in the same fixed microscopic field of view for the whole clip; two distinct illumination phases are shown, one before and one after a switch; however the switch itself is shown as an abrupt cut rather than a continuous transition, or the field of view changes slightly between the two phases, or unrelated microscopy hardware (like a visible lens barrel or stage knob) appears in frame.
level_4: All of the score 3 criteria are present, and beyond them, cells are clearly visible on the glass slide in the same fixed field of view across both phases of the video; the illumination switch happens as one continuous transition with no cut, no fade to black, and no overlay graphic; the slide, cells, and background all stay in the same spatial position throughout; no extra labels, arrows, or on-screen text appear.
level_5: All of the score 4 criteria are present, and beyond them, the cells look like a plausible adherent culture (spread out, not aggregated into an unnatural clump), the illumination switch is achieved without any visible lamp movement, filter-wheel rotation, or shutter flicker breaking the shot, and the video shows zero spatial drift of the slide or cells and zero on-screen text or graphics at any point.

Scientific and Causal Correctness rubric:
level_1: Cells appear to emit light while still under white-light illumination; or fluorescence appears before the illumination switch happens; or cells glow without any excitation light being shown; or the fluorescence color shown doesn't match any real dye's emission (e.g. blue light coming out under green excitation); or the cells stay dark even after the excitation light comes on.
level_2: The illumination switches, but the cells don't change brightness; or the cells change brightness without any illumination switch; or the cells get brighter under white light and dimmer under excitation light (backwards); or the emitted color is physically implausible for the stated excitation; or something unrelated to the fluorescence transition happens on screen (cells dividing, moving, or bleaching) that isn't part of a static observation.
level_3: The cells go from dark to bright once the illumination switches, but the change is uneven: some cells brighten while others stay dark under the same excitation; or the emitted color looks washed-out and colorless rather than a recognizable hue; or the background glows more strongly than the cells; or the cells appear to move or change shape during the switch instead of staying still.
level_4: All the cells switch from dark to bright together once the illumination changes; the fluorescence color is a single, clearly recognizable hue (all green, or all red, consistently) across every cell; the background stays darker than the cells; the cells stay in the same shape and position; there's no fading or delayed brightening once the switch happens; the excitation-to-fluorescence connection is visually clear and unbroken.
level_5: All of the score 4 criteria are present, and beyond them, the switch from dark to bright happens for every cell at essentially the same moment the illumination changes, the fluorescence color matches a real dye-excitation pairing consistent with the setup (e.g. green emission matching the described excitation light), no unstained background region shows a stray glow, and there is no visible delay or unevenness in which cells light up first.

Spatiotemporal Consistency rubric:
level_1: Cells jump to a different spot between frames; the slide disappears and reappears; the camera view flips 180 degrees with no transition; the image suddenly zooms in or out with no camera movement shown; the screen goes fully black between the two illumination phases; cells appear to break apart or dissolve mid-transition.
level_2: The slide shifts sideways or rotates slightly between the white-light and excitation-light phases; the cells visibly jitter or wobble; the illumination switch causes a bright flash or bloom that hides the cells for more than a moment; the image blurs then sharpens as if refocusing; the background pattern changes noticeably; the video stutters as if frames were dropped.
level_3: The slide drifts only slightly (a small fraction of the frame width) between the two phases; there's a brief, subtle softening and re-sharpening of focus during the transition; the brightness across the frame shifts slightly in a way that suggests a moving hotspot; no cell or the slide itself jumps position or breaks apart; overall the field of view stays recognizably the same.
level_4: The slide and cells stay in the same position, orientation, and scale across both illumination phases; there's no focus shift, jitter, bloom, or moving shadow; the switch in illumination only changes brightness/emission, not the direction of shadows, the position of bright highlights, or the overall lighting falloff; the background looks the same in texture and contrast in both phases.
level_5: All of the score 4 criteria are present, and beyond them, every visible cell edge and slide edge appears to stay in the same place across every frame with no detectable drift, there's no motion blur that would be inconsistent with a completely still sample, no colored fringe or bleed appears along cell boundaries, and the illumination change affects only the brightness and color of the glow, not any secondary visual artifact like a shifting vignette, a new ring of light, or a color fringe at the edges of the frame.