Inkscape is a free and powerful image designing software. If however you want to draw a vector-based image in your own style, use Inkscape. For a small fee, you easily get a publication quality conceptual image. BioRender has a library of pre-made icons and templates that can easily be manipulated. If drawing scares you, Biorender is a place to go. It easily assembles multi-panel image, annotates them and places the all important scale bar. The FigureJ plugin leverages the tools available in ImageJ/Fiji to make scientific figures. For image analysis, manipulation and figure making These images are then assembled in a coherent figure, the format of which is dictated by the journal you want to publish in.

Conceptual images - usually an impactful drawing that summarises your findings.

Scientific images - taken from with a microscope or a camera.

from Pymol or protein/nucleic acid alignments from software such as SnapGene.

Graphical Data - these are mostly graphs, extracted from your statistical software of choice like SOFA or JAPS, but can also be 3D models of proteins eg.In biology, there are three kinds of images you need to consider:

Free powerful open source software are available to replace costly and often complicated commercial ones. This doesn't need to be a stressful nor expensive experience. Preparing scientific figures is an essential part of a research project where data preservation, readability and aesthetic need to be balanced.

Inkscape vs gimp scientific journals