Hi Diego,[br][br]thanks for giving us the possibilities to share our ideas for 3D printig.[br][br]So here are some suggestions:[br][list][*][b]staircase[/b]: [url=https://www.geogebra.org/m/vvAv2KGq]https://www.geogebra.org/m/vvAv2KGq[/url] [br][/*][*][b]Moebius strip [/b](twisted twice): [url=https://www.geogebra.org/m/gqy5ftug]https://www.geogebra.org/m/gqy5ftug[/url][/*][*][b]3 spheres[/b]: [url=https://www.geogebra.org/m/nEcXdxxA]https://www.geogebra.org/m/nEcXdxxA[/url][/*][*][b]corkscrew[/b]: [url=https://www.geogebra.org/m/Gun6mzyK]https://www.geogebra.org/m/Gun6mzyK[/url][/*][*][b]dam[/b]: [url=https://www.geogebra.org/m/u8HAbVZT]https://www.geogebra.org/m/u8HAbVZT[/url][/*][*][b]quadrics[/b]: [url=https://www.geogebra.org/m/JxkKWJFn]https://www.geogebra.org/m/JxkKWJFn[/url][/*][*][b]loudspeaker 1[/b]: [url=https://www.geogebra.org/m/D6YdEfkD]https://www.geogebra.org/m/D6YdEfkD[/url][/*][*][b]loudspeaker 2[/b]: [url=https://www.geogebra.org/m/Grj6HhHg]https://www.geogebra.org/m/Grj6HhHg[/url][br][/*][*][b]buccoli[/b] (a kind of pasta): [url=https://www.geogebra.org/m/VXMuygWp]https://www.geogebra.org/m/VXMuygWp[/url][/*][*][b]electric potential[/b]: [url=https://www.geogebra.org/m/xJ9dZkXp]https://www.geogebra.org/m/xJ9dZkXp[/url][/*][*][b]methan molecule[/b]: [url=https://www.geogebra.org/m/xw2Vw347]https://www.geogebra.org/m/xw2Vw347[/url][/*][*][b]DNA[/b]: [url=https://www.geogebra.org/m/xtArgxZ9]https://www.geogebra.org/m/xtArgxZ9[/url][/*][*]...[/*][/list]