<p>Solid-state silicon transistors have profoundly transformed modern life by enabling a wide array of electronic technologies. The rise of bioelectronics has emphasized the necessity for interfacing transistors with living systems. However, challenges such as mechanical incompatibility, disparities in charge carrier types and differences in form factors present significant barriers to seamless integration. Recent advances in hydrogels have led to the development of hydrogel transistors, which merge the unique properties of hydrogels with transistor functionality, offering a solution to overcome these mismatches. This Perspective highlights hydrogel transistors, their biomimetic features and methods for their fabrication and characterization. We envision how hydrogel transistors, by evolving from conventional 2D thin-film electronics to 3D gel electronics, expand the device toolbox, enabling next-generation 3D, programmable and living bioelectronics.</p>