What is the fine-grained topic of the following text: Each of the four artists invited to exhibit – Koby Martin, Eman Unaji, Wipbee and Buki Kekere – were and are wavy in their own right and are very much on an upwards trajectory. Only return the topic.
Exhibition and growth of four artists: Koby Martin, Eman Unaji, Wipbee and Buki Kekere.