Sponges (Porifera), basal nonbilaterian metazoans, are well known for their high regenerative capacities ranging from reparation of a lost body wall to whole-body regeneration from a small piece of tissues or even from dissociated cells. Sponges from different clades utilize different cell sources and various morphological processes to complete the regeneration. This variety makes these animals promising models for studying the evolution of regeneration in Metazoa. However, there are few publications concerning the regenerative mechanisms in sponges. This could be partially explained by the delicacy of sponge tissues, which requires modifying and fine adjusting of common research protocols. The current chapter describes various methods for studying regeneration processes in the marine calcareous sponge, Leucosolenia. Provided protocols span all significant research steps: from sponge collection and surgical operations to various types of microscopy and immunohistochemical studies.