A method performed by one or more computers, the method comprising: receiving an input image from a target domain; processing the input image from the target domain using a shared encoder neural network, wherein the shared encoder neural network is configured to: receive the input image from the target domain; and process the input image to generate a shared feature representation of features of the input image that are shared between images from the target domain and images from a source domain different from the target domain; and processing the shared feature representation of the input image from the target domain using a classifier neural network, wherein the classifier neural network has been trained on labeled images from the source domain, and wherein the classifier neural network is configured to: receive the shared feature representation; and process the shared feature representation to generate a network output for the input image that characterizes the input image; wherein the shared encoder neural network has been trained to generate shared feature representations for input images from the target domain that are similar to shared feature representations for input images from the source domain; wherein the shared encoder neural network has been trained to generate shared feature representations for input images from the target domain that are different from private feature representations for the same input images from the target domain generated by a private target encoder neural network that is specific to the target domain; wherein the shared encoder neural network has been trained to generate shared feature representations for input images from the source domain that are different from private feature representations for the same input images from the source domain generated by a private source encoder neural network that is specific to the source domain; wherein the shared encoder neural network has been trained to generate a shared feature representation for an input image from the target domain that, when combined with a private feature representation for the same input image generated by the private target encoder neural network, can be used to accurately reconstruct the input image by a shared decoder neural network; and wherein the shared encoder neural network has been trained to generate a shared feature representation for an input image from the source domain that, when combined with a private feature representation for the same input image generated by the private source encoder neural network, can be used to accurately reconstruct the input image by the shared decoder neural network. receiving an input image from a target domain; processing the input image from the target domain using a shared encoder neural network, wherein the shared encoder neural network is configured to: receive the input image from the target domain; and process the input image to generate a shared feature representation of features of the input image that are shared between images from the target domain and images from a source domain different from the target domain; and receive the input image from the target domain; and process the input image to generate a shared feature representation of features of the input image that are shared between images from the target domain and images from a source domain different from the target domain; and processing the shared feature representation of the input image from the target domain using a classifier neural network, wherein the classifier neural network has been trained on labeled images from the source domain, and wherein the classifier neural network is configured to: receive the shared feature representation; and process the shared feature representation to generate a network output for the input image that characterizes the input image; receive the shared feature representation; and process the shared feature representation to generate a network output for the input image that characterizes the input image; wherein the shared encoder neural network has been trained to generate shared feature representations for input images from the target domain that are similar to shared feature representations for input images from the source domain; wherein the shared encoder neural network has been trained to generate shared feature representations for input images from the target domain that are different from private feature representations for the same input images from the target domain generated by a private target encoder neural network that is specific to the target domain; wherein the shared encoder neural network has been trained to generate shared feature representations for input images from the source domain that are different from private feature representations for the same input images from the source domain generated by a private source encoder neural network that is specific to the source domain; wherein the shared encoder neural network has been trained to generate a shared feature representation for an input image from the target domain that, when combined with a private feature representation for the same input image generated by the private target encoder neural network, can be used to accurately reconstruct the input image by a shared decoder neural network; and wherein the shared encoder neural network has been trained to generate a shared feature representation for an input image from the source domain that, when combined with a private feature representation for the same input image generated by the private source encoder neural network, can be used to accurately reconstruct the input image by the shared decoder neural network.