(a) A dynamically polymerizing actin network, branched with arp2/3, bound to the outside of a GUV was shown to be sufficient to induce both inward ‘spike'-like protrusions and outward membrane deformation in the form of tube formation [24]. (b) Inward and outward deformation was also created through control of reaction kinetics, using capping proteins, in arp2/3 branched networks bound to the inner leaflet of a GUV. The nature of deformation depended solely on the capping protein concentration, with protrusions occurring at low capping protein concentrations, transitioning to invagination-like deformations at higher concentrations [49]. (c) Inner-membrane-bound actin networks with fascin and arp2/3 adopt bundled and dendritic morphologies whose ability to form protrusions is a direct consequence of the relative concentrations of the two binding proteins [50]. (d) The formation of contractile actomyosin ring-like structures was achieved through a combination of fascin-induced bundling and myosin-induced contraction in inner-leaflet-bound actin networks [21]. Here, yellow lines indicate the approximate fascin bundle position. All scale bars are 5 µm unless otherwise stated.