x3
x and y +
X chromosome +
X and X chromosomes +
X and Y chromosomes +
x-axis and y-axis graph, a +
x-rated movies -
x-ray astronomy +
x-ray crystallograph of DNA molecules, a +
x-ray crystallography +
x-ray diffraction pattern, a +
x-ray image, an +
x-ray machine, a +
x-ray photograph of DNA +
x-ray scans +
x-ray shadow, an -
x-ray telescopes +
XY sex-determination system +