Soap Bubbles
His lady's smiles are beautiful but rare and ephemeral, even now. Oh, her pretty lips will curve upwards in a smirk easily enough, and he likes those, too. She is beautiful no matter what she does, even covered in grime and screaming insults at enemy and ally alike.
But smiles – real smiles, when her entire frame seems to shimmer and glow from within and unadulterated happiness overflows from her spark for a few tantalizing cycles – are as rare as transits of Venus and as fleeting as soap bubbles, and more precious to him than all the Energon in the universe.
A/N: 100 words; written for the prompt 'soap bubbles'.
Silverbolt is exaggerating: transits of Venus (when Venus is visible as a shadow crossing the Sun's face as it passes directly between the Earth and Sun) occur in a pattern that repeats every 243 years of four transits per cycle.